MTG Salvation

Why does he look sinister here? He's giving me Disaster Girl vibes

Could be the Blackblade's influence. (Dakkon, where are you? Gideon's going to need your help...)

To be clear, this can be used as soon as attackers have been declared?

This can be cast at any point in the turn when you gain priority, which means you could cast it before combat (to no effect,) after attackers have been declared but before blocks, after first strike damage but before normal damage, or after combat has finished resolving (after blocks have killed smaller attackers, for instance.) Seems pretty good to me.