Loki's "I am a GOD!" timing on defense.

[Ludo Chose]

"Before rolling attack of defense dice you may use this power. During this attack, this character adds blanks in its attack or defense rolls to its total succcesses."

If Loki is defending against an attack, since the attacker rolls first, do Loki gets to use this reactive superpower before or after the attacker's roll?

[Negoldar]

I am a GOD! is used at the beginning of step 6 when attacking and beginning of step 7 when defending.

Yes, you can see the attacker's roll before deciding. After you decide and roll defense dice the attacker can resolve any criticals.