This dungeon is crucial for farming talent upgrades, and thankfully, the early stages aren't too tough. The main thing you need to worry about is cleansing Burn status effects. Since this dungeon specifically counters Fire and Poison attributes, your best bet is to use the free hero, Catherine. Unleash her Ultimate before the boss uses theirs to give your whole team Immunity to debuffs. Garius can actually cleanse debuffs on himself, so he doesn't need special attention here.
Here's the recommended positioning: The recommended team is shown above, featuring Ladehlia and Isitarian. This setup lets you leverage your summoned units to quickly clear the dungeon. Just be sure to pay close attention to when you use Catherine's Ultimate skill. Since all these characters are free, it's a super easy team to put together and complete the dungeon with. If you manage to get Acilia, you can swap her in for Catherine. For the second phase, save Catherine's Ultimate. Then, activate it right before you enter the third phase to prevent the boss from applying the Burn status effect. For the second phase, save Catherine's Ultimate. Then, activate it right before you enter the third phase to prevent the boss from applying the Burn status effect.