User blog comment:B214/Talk About What You Want! 2/@comment-117.195.112.194-20140710192732/@comment-24098614-20140710201929

Fenrir is one particular monster that Gods need boyguards from because read your Norse Mythology Fenrir killed Odin in Ragnarok, and the Midgard Serpent killed Thor in that fated battle those monster are insanely powerful, and both of them played a role in that prophecy to end the Norse Gods.

The Norse Gods have extremely dangerous monsters roaming their Realms even Issei  would be killed immediately, and this is not even mentioning Surtur and Ymir who are the two most powerful Giants to ever lived in fact Surtur posesses a Sword that can destroy a world.