Chameleon

Chameleon is able to freely change its element by going to its pet page. After you evolve it, Chameleon will count as the correct element for dungeon events regardless of the element you have made it.

Evolving Details
All of the dungeons need to be done at D2 for 48 rooms, meaning no traps/events triggered causing you to lose any rooms or you will fail this requirement. Chameleon does not need to be in the dungeon to get credit added towards the evo. These dungeons will only start counting after you have unlocked Chameleon first and you can check which dungeons you still need by attempting to evo assuming you meet the other requirements. For more information on the fight, see here: Chameleon Boss