Sandile is available in both Black and White on Route 4, in the Desert Resort and the Relic Castle. Krokorok can also be found in the Relic Castle. The encounter rate is 40% in the first two cases, and 50% in the last two. Sandile can only be found on 1F and B1F, whereas Krokorok may be found on the other floors.
Known for its remarkable offensive power and its relatively early availability in the game, Krookodile is possibly one of the most popular Pokémon amongst Unova nuzlockers, and for a good reason. The hardest part of training up one is taking the frail Sandile up to Krokorok level; after that, for Eviolite carriers, getting to the final evolution stage is not hard, although the level curve in Black and White makes it difficult before the late game. However, it is entirely worth it: the Dark-type is amazing in battle, and almost single-handedly wrecks the last few bosses, as well as STAB Earthquake being powerful and very useful in general. Despite the many weaknesses, Krookodile can perfectly hold its own and do much more, and is overall a really solid choice for beginners and experienced players alike.
Gym #3 - Burgh (Castelia City, Bug-type): While the typing alone might make this seem a very bad matchup for Sandile, this gym is actually less threatening than it looks, due to Burgh's signature move being Struggle Bug. Of course, Leavanny's almighty STAB Razor Leaf is to be avoided, but otherwise Sandile can attempt to fight him if the Eviolite is being held. Whirlipede will be tough, especially with poison hax induced by Poison Tail thrown in the mix, but Sandile can overcome it if supported by Antidotes; Dwebble is very manageable, since Sandile resist everything it has except for Struggle Bug. Dig away.
Bianca (Castelia City): Herdier's STAB Take Down is dangerous for the frail Sandile, but an Eviolite carrier can actually take two of them and, if lucky with Bite flinches, eventually take down the enemy despite Intimidate. All three starters mean immediate death for it, however, due to their STABs (Pignite has Arm Thrust). Pansage and Panpour are a bit less powerful, but there is no underrating super effective STAB moves and Sandile is better off leaving the battles to a more appropriate teammate. Pansear and Munna are the only opponents Sandile can fight safely.
Cheren (Route 4): His lead Pidove is not threatening overall, despite the Super Luck-affected Air Cutter, and can be nailed with Bite in two hits (sometimes three, with low damage rolls); of course, if Sandile no longer knows the move, it is going to take an extra turn, adding up to the damage Sandile will take. Liepard is best avoided: Sand-Attack and Fury Swipes are a deadly combo for Sandile, at least at this point in the game; while Pursuit on the switch will only do half thanks to Sandile's resistance, there are likely better options to take care of Liepard. The same goes for the Grass-type and Water-type elemental monkeys and starters. Pansear is easy with a Ground move, but Pignite has Arm Thrust; stay away.
N (Nimbasa City): Sandile and Darumaka are easy fights since Sandile has access to Dig, but do not try fighting Scraggy, which already has Brick Break. Sigilyph, while being at a type disadvantage, has high Special Attack at this point in the game, and Air Cutter to back it up; it will also outspeed Sandile, and combined with the high critical hit ratio, its moves are definitely not something Sandile wants to take. However, if lucky, an Eviolite Sandile can 2HKO it with Bite, as Air Cutter is only a 3HKO without any critical hits.
Gym #4 - Elesa (Nimbasa City, Electric-type): Sandile is definitely at risk in this gym, though if it has evolved it into Krokorok already, everything will be much easier. The two Emolga will be a pain, and it is advised to not use anything but Crunch until they are both down, as the AI will likely switch in to the other Emolga even if Sandile is against Zebstrika and uses Dig. Only the Sand Tomb + Dig combo is guaranteed to make Sandile defeat Elesa in peace, but Sandile will likely need multiple heals due to the Emolga's STAB Aerial Ace. Zebstrika will also definitely outspeed both Sandile and Krokorok, and annoy them with a likely flinch-inducing Stomp; even if it does not outspeed on the first turn, Flame Charge will allow it to do so after just one use. As Sandile gets 3HKOed by anything on Elesa's team even with the Eviolite, having an Eviolite Krokorok is recommended; it can take far more hits, and scores 2HKOs all across the board with Crunch.
Cheren (Route 5): Pidove evolved into Tranquill and got just a little more threatening in the meanwhile. With a Sandile, most of his team is off-limits, Pansear and Tranquill excluded (paying attention to Tranquill's possible critical hits); however, if Krokorok is already evolved, Liepard becomes a lot more manageable, and so does the bird. The considerations for the Grass- and Water-types still hold, though, and same for Pignite: they are a bad idea and a better counter should be found for them.
Gym #5 - Clay (Driftveil City, Ground-type): Another pretty good matchup overall. Krokorok is easily mirrored, and it does not have Dig, which is a 2-3HKO from the ally Krokorok; just pay attention to Swagger if it uses it - and it may paradoxically be better if it does, since its Intimidate greatly hinders Krokorok's offensive power. If there are Casteliacones handy, Krokorok could actually exploit Swagger to get Attack boosts, but since Clay will surely send in Palpitoad later it is probably pointless unless Krokorok gets Swaggered at least twice. It goes without saying that Krokorok will not want to tank Palpitoad's STAB BubbleBeam, so leave that Pokémon to someone else. Bring it back in for the ace, Excadrill, which is very powerful but also weak to Ground. STAB Dig will do wonders against it, and with Intimidate, its Bulldoze goes from 3HKO to 4HKO, with Krokorok's Dig being a 2HKO with neutral Attack; however, Excadrill can also boost its Attack with Hone Claws, and will flat out OHKO Krokorok (with the Eviolite) starting at +3 Attack. Play carefully.
Bianca (Driftveil City): Since Krokorok is most likely evolved by now, it can tackle Herdier more safely, particularly if it holds an Eviolite and/or has Intimidate to back itself up. Keep in mind, however, that Herdier has that ability as well, and Bianca has two Hyper Potions; chances are Krokorok will need healing up in this battle too, so go there prepared. The elemental monkeys have become fairly viable thanks to Krokorok being evolved and still getting the Eviolite boost, but Servine and Dewott remain too tough to take on.
N (Chargestone Cave): A wonderful battle for a Krokorok to take part in, as basically everything in its team will crumble down to Ground STAB. Ferroseed can stand up to two hits, but it does not have Grass moves, and the other Pokémon are not half as threatening either.
Gym #6 - Skyla (Mistralton City, Flying-type): Although all of Skyla's Pokémon are immune to Ground, Krokorok does have another STAB to play with. Swoobat is fast and has STAB Acrobatics, but its Attack is not really sky high and Crunch is a certain OHKO, unless Krokorok has subpar Attack; Unfezant cannot exploit crithax at all, since it only has special moves (and Quick Attack, technically, but it is very weak) and Big Pecks instead of Super Luck. A Krokorok armed with patience can Crunch its enemies to victory, in an average of three hits. Swanna, however, is another story. Awesome though the croc is, yet another STAB BubbleBeam is not for Krokorok to take. Fry it with any Electric Pokémon, or wear it down with a special wall.
Cheren (Route 7): Unfezant's Super Luck + Scope Lens combo may be scary, but its Special Attack can at best 3HKO an Eviolite Krokorok at this point. Liepard is laughable, thanks to Fake Out and Assurance now being its only offensive moves, so Dig away. Simisear is safe to handle too, and so is Pignite now, thanks to its lack of Fighting moves. As usual, Krokorok should steer clear from both of the other monkeys and starters.
Gym #7 - Brycen (Icirrus City, Ice-type): While Krokorok is certainly a great Pokémon, having it participate in this gym battle would be pushing its luck. This gym is not for it. The only Pokémon Brycen has that Krokorok can attempt to tackle is Cryogonal, because it is very physically frail and there is a Brick Break TM available in the Icirrus City Pokémon Center, which may net the OHKO if Krokorok's Attack is good and/or it lucks out with the damage variation. However, keep in mind that Cryogonal is also very fast - it has a higher base Speed than Krookodile - and can OHKO an Eviolite Krokorok with a critical Aurora Beam (though not with Frost Breath). Other than that, stay the hell away from both Vanillish and Beartic, especially the latter, since both of them are only waiting for the right chance to freeze Krokorok dead.
Bianca (Route 8): Bianca has a Retaliate Stoutland, and its ability is Intimidate. Assuming Krookodile is already fully evolved, it can outfight Stoutland with some patience, but its Intimidate turns Brick Break from a 2HKO into a 3HKO. Regardless, it can 3-4HKO with Retaliate at best, depending on whether Krookodile has Intimidate or not; Krookodile is safe in either case. Avoid her Grass- and Water-types like the plague; feel free to tear into Musharna and the Fire-types, though, as Emboar no longer has Fighting moves and it should be paradoxically easier to defeat now.
Gym #8 - Iris/Drayden (Opelucid City, Dragon-type): The only difference in their teams is Druddigon's ability: Drayden's Druddigon has Rough Skin, whereas Iris' has Sheer Force. Their whole team is fairly threatening, due to Fraxure and Haxorus both having Dragon Dance; a Krookodile with Intimidate is much better for switch-ins, although if Krookodile must carry the team through for the whole fight, Moxie is certainly better, if not outright needed for survival. Crunch can 2HKO Fraxure, before it gets to do much of anything; if Krookodile's Speed is above 100, it is also unlikely that Fraxure will outspeed after a single Dragon Dance. Druddigon has Revenge, and even though Krookodile has enough bulk to take one, a critical hit will definitely kill. Moxie is not sufficient to OHKO either; only at +3 Attack or more can Krookodile be certain that Crunch will one-shot Druddigon. For Haxorus, the only way to get past it without significant damage is having some setup first. Two X Attacks are recommended if Krookodile has Intimidate, or if something else was used to defeat the first two Pokémon; Haxorus will hurt a lot and has the potential to crush everything in sight with just one Dragon Dance, let alone two. Krookodile's Crunch is a 3HKO in its natural state, and can OHKO at +3 or +4 Attack, depending on its stats; however, if Haxorus goes for just one Dragon Dance and then starts attacking, Krookodile will be dead in two hits, just before dealing the finishing blow.
Cheren (Route 10): Crunch will do Unfezant in, since its moveset is entirely special, and Krookodile's Ground STAB of choice (presumably Dig) will take care of Liepard and Simisear or Emboar just fine. Emboar does not have Fighting moves, though it does have powerful Fire STAB, so do not underestimate it if Krookodile is at low health; Dig is not an OHKO, unless Krookodile has a Soft Sand or Expert Belt and lucks out with the damage roll. As far as this fight goes, this is where Krookodile's contribution ends; just like before, hoping to tackle any of his other (Grass and Water) Pokémon with Krookodile and keeping it alive at the same time is far too risky, and there should be better counters by now.
Elite Four Shauntal (Pokémon League, Ghost-type): This matchup could not get any more excellent. While Jellicent's Surf might make a dent in the croc's special bulk, none of Shauntal's Pokémon pack anything that is more powerful than Krookodile's STAB Crunch, so Krookodile can trash her team completely. One thing to be wary of, however, is Jellicent's Cursed Body, which might disable Crunch and leave Krookodile out of options to fight Golurk and/or Chandelure; in order to avoid this, give Krookodile the Expert Belt, which will secure the OHKO against Jellicent and reduce the possibility of Cursed Body activating down to a minimum. Cofagrigus is the only one that can take a Crunch and live, but its Grass Knot has extremely low chances of killing Krookodile even with a critical hit.
Elite Four Marshal (Pokémon League, Fighting-type): None of the moves that Krookodile learns can be of relevant use here, not even Aerial Ace, and there is so much in Marshal's team that can hurt Krookodile badly that it really, really should not fight anything he has.
Elite Four Grimsley (Pokémon League, Dark-type): The problems here are Scrafty and Bisharp. Scrafty is bulky and has Fighting STAB, but Krookodile's Brick Break can actually 2HKO it with the Expert Belt attached; however, a critical hit from it will off Krookodile. Bisharp has X-Scissor and remarkable bulk; however, Brick Break OHKOs Bisharp easily unless Krookodile's Attack is very low, in which case Krookodile should be wary of its Defiant in case it is switching in and has Intimidate. Brick Break also 2HKOs Grimsley's Krookodile and OHKOs Liepard.
Elite Four Caitlin (Pokémon League, Psychic-type): Her lead, Reuniclus, has a very threatening Focus Blast, but an Expert Belt Krookodile might OHKO it with Crunch, depending on its Attack stat. A Dark Gem will do that for certain, and might be the best option for Moxie Krookodile, as they can OHKO everything Caitlin has after a single boost. The movesets of the others are not really scary; Sigilyph has Ice Beam, but it only becomes a problem around half health or below, and Crunch OHKOs it; Gothitelle is hard to OHKO if the croc's Attack is not high and it has Intimidate, but the best it can do against Krookodile is use Shadow Ball, which deals laughable damage.
Reshiram/Zekrom (N's Castle): Krookodile's Earthquake is the best ally for this fight, and will deal with both Reshiram and Zekrom just fine in at most two hits. With the Expert Belt, the OHKO is guaranteed unless Krookodile's Attack is below average, and even if it is, the Ground Gem will fix that.
N (N's Castle): Krookodile will turn out incredibly helpful again here, as it is one of the very few Pokémon in the game that can face both Tao dragons without fear. Earthquake will easily 2HKO them, or even net the OHKO if, once again, Krookodile has an Expert Belt or Ground Gem handy (mind that fighting Reshiram or Zekrom will consume the latter, and there is no way of restoring it). As far as the rest of his team goes, the only two members to critically avoid are Carracosta (which also has Sturdy, so Krookodile cannot hope to knock it out in one hit whatsoever) and Vanilluxe, both of whom will most definitely NOT die in a single move; sure, Krookodile may have Brick Break, but Vanilluxe has more than enough bulk to take one, and Blizzard is deadly if it hits. Brick Break or Earthquake will, however, prove themselves useful against Zoroark and Klinklang, considering however that Zoroark has Focus Blast and Illusion, a combination that will put a dent in Krookodile's health or even kill with a critical hit. Archeops will easily die to two Crunches, though STAB Acrobatics is no fun and the ideal way of dealing with it would be something that carries Aqua Jet, or making sure that Krookodile can outspeed, which is possible with a Speed-boosting nature or other Speed investments. Overall, Krookodile can put some good work in here, but its health needs to be kept high to avoid awful surprises.
Ghetsis (N's Castle): For a fight that is nothing short of awful, Krookodile actually fares very well. Cofagrigus has annoying Toxic stall capabilities, but its only offensive moves are Psychic and Shadow Ball, neither of which will do a lot to the sand croc; as such, it can take advantage of the low damage output of its enemy to start stacking Attack boosts undisturbed. At +3 Attack or higher and the Expert Belt handy, Krookodile can OHKO everything on Ghetsis' team with either Earthquake, Crunch, or Brick Break; Moxie specimens will need to get to +3 before Cofagrigus goes down in any case, otherwise Ghetsis will likely throw Seismitoad in and ruin Krookodile's setup plans. Without the Expert Belt, Krookodile may actually need an additional Attack boost to secure victory against all enemies, but once again this depends on its Attack stat.
Post-Game: Krookodile still has the type effectiveness on its side, and it will turn out very useful against the League during the rematches. Legendary Pokémon are another thing, but in general terms, a Krookodile used sensibly will not be in danger often, if at all.
When caught at its earliest levels, Sandile knows Sand-Attack, Torment, Sand Tomb, and either Bite or Assurance. Bite is marginally better, and the other moves are all fairly useless. The upside is that the TM28, Dig, is nearby, so Sandile will get access to a great move very soon. By level, it will not get much for a while: Mud-Slap at level 19, which will barely deal any damage to enemies; Embargo at 22, which Sandile will basically never ever use; Swagger at 25, which is one of the worst possible gambles due to the line's frail defenses until Krookodile status, but might actually work mildly well on an Intimidate Sandile; and finally, Crunch at 28, which will become Sandile's best STAB as soon as it gains access to it. Together with Dig, which Sandile can get at level 32 after evolving into Krokorok if the move was not taught via TM for some reason, it will be everything Krokorok needs for a good, long while. Ignore Scary Face at 36, as this line is fairly fast on its own, and Foul Play at 40 is something that could only be of any use on a crocodile with very low Attack, because otherwise Crunch is always going to be stronger. If Krokorok somehow missed out on it and needs to learn it as Krookodile, it will get it again at level 42. Sandstorm comes at 48, and might work very well in monolockes or otherwise type-limiting challenges for support purposes, but nothing more than that; Earthquake, at 54, is the main dish of this line (and of every other Ground Pokémon ever) and will wreck everything in sight. Last but not least, Outrage arrives at level 60, if Krookodile ever gets that far; the postgame has a good few dragons, so Krookodile should definitely consider learning it, though Earthquake will work better for the Tao duo.
The choice is fairly vast even TM-wise. Dig, as mentioned, is accessible from early on without a need to wait for the level-up learning, and will do a lot of damage well until Earthquake level. Both Rock Slide and Stone Edge provide useful extra coverage to hit Flying-types, and Krookodile should definitely carry one of them; the choice between having better accuracy or better base power is up to the player, but accuracy should be favoured. It is worth noting that Krookodile can also learn Hone Claws, and with one setup turn, Stone Edge becomes much more viable. Brick Break also works well for coverage, and Dragon Claw is a more than valid alternative to the more risky Outrage, especially if Krookodile will not be levelled up enough to learn Outrage naturally. Consider Bulk Up for support, as it will work especially well on Intimidate specimens.
Recommended moveset: Bulk Up / Hone Claws, Earthquake, Crunch, Rock Slide / Stone Edge
Flying-types: The very common Flying-types cover for most of Krookodile's weaknesses very well. Late game Flying-types are recommended if available, since they will be more capable against Marshal; more generally, a Flying-type that does have a Fighting resistance should be preferred over a Normal/Flying-type or other dual types neutral to Fighting.
Water-types: With Krookodile and a Flying-type on board, the Ice weakness becomes worse, and further help against Water-types may be needed at a point in time. For this reason, aside from a Flying-type teammate, Krookodile should also be backed by a Water-type, preferably one that is resistant to both Water and Ice moves.
Minimum stats are calculated with 0 EVs, IVs of 0, and a hindering nature, if applicable.
Maximum stats are calculated with 252 EVs, IVs of 31, and a helpful nature, if applicable.
Sandile Line Ratings
What Nature do I want? Anything that lowers Special Attack is great, Adamant obviously being the best. Jolly is second best, and will likely allow the sand croc to outspeed almost anything in sight. Naughty is also okay, and better than Lonely since Intimidate Krookodile has remarkable physical bulk.
Which Ability do I want? The Sandile line is rather unique in that both of its available abilities are absolutely amazing. Intimidate allows it to function as more of a physical tank and also gives it more switch-in opportunities. Moxie, on the other hand, turns Krookodile into a fearsome sweeper that can take down whole teams with ease: two of the four Elite Four members (Caitlin and Shauntal) get completely demolished by Moxie Krookodile.
At what point in the game should I be evolved? As soon as possible. Ideally, Krokorok should be evolved around the time Elesa is fought, and Krookodile shortly after the Brycen fight. Sandile is really frail; Krokorok can hold its own with the Eviolite until evolution, and the item is highly recommended to prevent untimely deaths.
How good is the Sandile line in a Nuzlocke? It has fantastic STAB, gets overpowered moves from relatively early levels and also has great TM support to back that up. On top of that, the Dark typing alone is incredibly useful in the late game. Krookodile is a top class Unovan in countless ways, and entirely worth training up.