|This spell infuses the caster's melee attacks with magic, drawing from their reserves of magical energy to deal additional damage whenever an enemy is hit. It has no effect when the caster's magic is depleted.|
Infusion is a level 1 Charms spell which temporarily causes your melee attacks to deal 2-4 more damage at a cost of 1 MP per hit. This additional damage is reduced by AC separately from your normal attack. Infusion will not activate as long as you have 0 MP remaining, but will resume its effect once you've regenerated at least 1 MP.
While it's nice to have a level 1 spell that gives you a pseudo-slaying bonus, be aware that it can chew through your MP reserves quickly, and that the additional damage will have little impact against enemies with even modest AC. It can help you deal quick damage to threats in the early game, but don't expect it to help much against orc warriors and the like.
Infusion was added in 0.13.