User blog comment:B214/Volume 21 info & spoilers/@comment-222.124.122.111-20160626015201

Speaking of Norse Mythology. Did Thor seal himself besides Odin and other Norse Gods or Thor become Odin sucesssors as Chief of Norse God? And what about Loki's fate after Odin and other Gods seal themselves to stop Trihexa?

For my theory Loki heard some information that the Norse Factions seal themselves to stop Trihexa (including Odin and other Norse Gods).

Then, he uses this oportunity to break the seals, kills the Asgardian Guards, and escapes nowhere. Loki also wants to take a revenge against Issei/Sekiryuutei and his friends for what they've done to him on LN Volume 7. He swears that he will curses Issei and his important friends/lover one day. That's why Loki in the future become main villain/antagonist in DxD EX and the enemies of Issei's children especially Ex Gremory.