Relic Castle Pokémon
- Baltoy - Common, Walking, All Seasons - Volcarona's room only
- Krokorok - Rare, Walking, All Seasons
- Sandile - Common, Walking, All Seasons
- Sandslash - Uncommon, Walking, All Seasons
- Yamask - Common, Walking, All Seasons
... unless, of course, you opt to come through via Relic Passage. Do that and you'll discover that sections of Relic Castle are still alive and kicking, and there are yet treasures for the relentless hunter.
At the end of a lengthy hall you'll find the main reason for coming down here: Volcarona, a Fire- and Bug-type Pokémon that's enormously powerful, and a great addition to any team. It's especially good against the current members of the Elite Four, as its Bug-type STAB moves are super effective against two of them. Catching it is highly recommended...
... though when you catch it is a matter for debate. You should fight the Volcarona when you come down here either way; if you so desire, however, you can beat it now and then come back for it after you've beaten the Elite Four. Doing so will propel its level from 35 to 65, granting Volcarona access to much more powerful moves than it currently has. This will save you a lot of raising time... though from an EV point of view, catching Volcarona now and putting it through EV training immediately will give you many more levels to improve its stats. The choice is, ultimately, yours.
Volcarona aside, you may want to snag a Baltoy while you're down here. They're powerful Pokémon, and they pop up constantly while you're in Relic Castle - and nowhere else in the game. Once you've grabbed all the occupants of this room, however, there's not much point to the Relic Castle. Head back to Relic Passage and the surface to continue your journey.