Battle Chasers: Nightwar

Story related, can not be missed.

You must make your way to The Dig in search of the Dead Heart so you can make it through the Southern Gate. For the Dig you just need to make it to the final elevator that takes you to the lowest level and then fight the boss Cadaverous Mound, a giant slime monster. His main attacks are a blob spit that causes a random debuff and a mist that does multiple hits to the characters while adding debuffs as well. When he takes enough damage, he will split into additional slimes and his health will go back up a little. After you defeat him and end The Dig quest, the trophy will pop.