Really easy, I expected more difficulty from the second to last boss.

All you have to do is position the Maiden correctly and stay away.
The boss spams an AoE that does almost no damage, and the boss itself doens't stack any kind of damage increasing debuff, allowing you to stay at range as long as you want.

I cleave the Maiden at start to lower her HP a bit because otherwise I would have to focus her at some point which would increase the length of the fight.

Music : Yttrium - Inspire
https://soundcloud.com/argofox/yttriu...

Enjoy :)