Chapter 352: Mark of the Seven Sins P2

"This is the true reward for clearing the first floor of the tower, Eren. You will receive a mark as you keep on clearing the floors.

... The mark of the Seven Sins."

Eren caressed his chin after he heard that. He was about to ask what the mark was. And how would it benefit him? But turned out he didn't need to because Eliza told him about them on her own:

"The marks let you tap into other planes and use their mana powers for your own. As for the specific benefits or disadvantages, they grant to the ranker, they may vary as per the rankers themselves.

Fufufu! I'm sure you'd be more compatible with using the mark than anyone else I've known. Because you were already seen using another plane's mana as your own."

Eliza clarified and created more questions in Eren's head. He decided to ask the most pertinent question first - what was its purpose. The Sage answered right afterwards: