Check your stats

You take a moment to pull up the level up menu, having never seen it before.

Lv 1-2
HP 15-20
MP 20-30
Atk 1-1
Def 0-0
Mat 2-4
Mdf 1-3
Agi 2-3
Skills:
Illusion: 10 MP Temporarily conceals the user from enemies. Lasts for 5 seconds for every point of the user's Mat minus 1 second for every point of the enemy's Mdf.

New Skills:
Soul crush: 10 MP Temporarily lowers the opponents Mat and Mdf by 50% lasts for the duration of combat.

To think you had such an op skill hiding just at level 2.

Normally, once there are no heroes in an area, the monsters reset. However, as a dungeon, it doesn't reset the map until it's cleared. Come to think of it, a boss may be challenged by a lesser monster for their position. It's rare, but you've heard of it happening before. Being a boss, you receive a 50% stat boost and a unique aura ability.

The boss in this dungeon is level 3. If you're lucky, you could claim his position. You know his attacks use Mat, and you could cancel the stat boost there with your soul crush ability. It's the aura effect that troubles you. You've never thought to check what it does.

The tank may come back, heroes tend to never give up on a challenge. Maybe you should wait and level up again. She'll probably be more prepared though. And may bring a friend or two.