Marenian Tavern Story: Patty and the Hungry God

I got this achievement with Lv. 99 Stella, dealing around 13000 damage against the green slimes with her Vanish skill in the first area after completing everything else.

Mana Robe and Mana Boots gave me more magic attack. I also eated "Whole Fish Fin" for an additional 25+ MAT. Before using Vanish use Mental Concentration for a magic attack buff.

I also used Holy Staff and Mana Shield (near death was not active), but i guess Reaper Staff and a shield with an magic attack orb would be even more efficient, but should be not necessary.