Hideous Blow clarification

[Akroma666]

So I know this ability only triggers on one attack. But what about your off hand? Does that count as a new trigger?

Also, does it get bonus from the daggerspell mage spell damage?

[DM Narshe]

Only triggers once per round. So if your main hand attack misses and your secondary hits, that's when it'll trigger.

It's not a ranged touch attack so it shouldn't gain bonus dmg from Daggerspell Mage.