Marvel's Greatest Warden

I see. I contain. I have never failed, and I will never run away!

Mason arrives in the perilous Marvel Universe with his containment facility and magical knowledge from another world, and puts down roots.

Sin is his finest sustenance, and knowledge his greatest treasure! He will put a chain around Thanos’s neck and pin Death’s shoulders down with iron shackles.

The Living Tribunal watches. Eternity draws near.

Mason sits in the sanctuary, murmuring:

“All things are equal.”

“Those who sin will be punished!”

[Update: The protagonist stops being human in the middle and later stages. Consider yourself warned.]

[Another update: Marvel only, no DC, no DC!!!]