Abyssus abyssum invocat

Abyssus abyssum invocat is the 5th volume in the Youjo Senki Light Novel series.

Short Summary
The power of blessing emerged in the surface.

Tanya and Mary sue have faced one another.

Who shall prevail?

Chapter VI: "Liberator"
That ends 500+ pages of vol 5.

Thanks to u/MSG_Johnny2 who posted the summaries at r/YoujoSenki.