might-quest-epic-loot should be
mighty, I think. How can I report the typo?
The best way is to post on meta as it allows people to point out alternative spellings or even that the tag has no typo (doesn't seem to be the case here). Moderators read meta (or at least I assume they do) so they will see it soon enough, and take appropriate action.
If the tag only has one or two questions and you have sufficient reputation, you can retag the questions and let the nightly tag cleaning script take care of the typo tag.