|Relic Castle B1F-B2F|
|Sandile||/||Lv. 18 ~ 21||40%|
|Yamask||Lv. 18 ~ 21||40%|
|Sandshrew||Lv. 19 ~ 20||20%|
Yamask is the first Ghost-type Pokemon you'll run into in the game. It has decent defensive stats, but lacks Speed and attacking stats for sure. It evolves into Cofagrigus at level 34, which is quite a bit of time to put up with Yamask's underwhelming stats. After evolution, it gets a whole ton of Defense as well as some very nice Special Defense and Special Attack, while remaining slow as a slug. It has the Mummy ability, which changes an attacker's ability to Mummy if it damages Yamask or Cofagrigus with a direct attack.
Yamask will have Hex to attack with when you get it, which is a 50 power Special-based Ghost-type attack, although its power doubles if the foe is affected by a status ailment. It gets Will-O-Wisp at level 21 to help boost Hex's power while also lowering the foe's Attack stat (due to the burn), and then it gets Ominous Wind at level 25 to hit for some damage but hopefully raise all of its stats by one stage (though only 10% of the time). Curse at level 29 is a gamble; since Yamask is a Ghost-type, it cuts its HP by half its maximum in order to inflict a curse to the target, which lowers their HP by 1/4 their maximum every turn. It can make up for Yamask's lack of damage potential, especially if you administer healing items afterwards. It gets Guard Split and Power Split at level 33; these moves are tricky, because they basically average out Yamask's offensive or defensive (depending on the attack used) stats with the target, giving them the same. Guard Split is better used on an ally while Power Split is better used on a foe, typically. Shadow Ball at level 39 (as a Cofagrigus) is probably the only worthwhile move for Cofagrigus, but you can learn that from a TM, too.
TM moves it gets are few and far between early on, but as you progress, it gets Shadow Ball (should learn it quicker than leveling up), Energy Ball, and Psychic. Toxic is a good move for it to whittle away at the foe's HP and, if you can get Protect from the Battle Subway or Pokemon World Tournament (it costs just 6 BP), you can use the two together.
I don't really recommend Cofagrigus. It lacks good moves early on, does nothing against Normal-type Pokemon, and is a pain to train up to level 34 to evolve it. Umbreon makes a better tank, even though it doesn't hit as hard as Cofagrigus, while Chandelure or Golurk are stronger Ghost-type Pokemon to use for that purpose. It's still not that bad or anything, but just doesn't stand out all that much.
Unless you want to fall down the sand pits, you're going to need to walk across them. This means no running! Avoid the first one and then cross the second one without running, fighting the Psychic with a Sigilyph L23. It's tough, but gives a lot of EXP when you beat it!
No Fossils for now...
In the previous games, you could talk to a person here and receive your choice of the Plume Fossil or Cover Fossil, which you could revive into a Archen or Tirtouga respectively. However, in Black 2 and White 2, you have no such free gift and have to wait until after you've beaten the game instead, where you can get them in Nacrene City. Oh well!
Head down the stairs and fight another Psychic, this one using a Gothita L23. Right past her is TM39 (Rock Tomb), a 50 power Rock-type attack that also lowers the foe's Speed after you use it. It has mediocre accuracy, though, but since a lot of non-Rock-type Pokemon can learn it, it can help add some diversity to your attacks and 50 power isn't that bad at this point in the game.
Now head back up the stairs and let yourself fall into the sand. You'll land directly on top of a hidden Heart Scale. Head on over east and fight the final Psychic, who uses a Solosis L23. Climb the stairs, jump down the ledge, and then make your way out of the Relic Castle.