Soma's teeth glare, then he steps forward and bites the target to restore HP and inflict high damage.
This move has short range (same range as the Slaughterer soul), but since each bite restores HP and does decent damage at high levels, this is a very useful soul. It is made even better by the fact that the effect works on candles, statues, and other furniture.
This soul is outshone by others in terms of combat effectiveness, but serves as a very useful means to restore HP, especially when used on furniture that drops hearts which help refund the cost of casting. This effect can be amplified when the succubus soul is used in conjuncion with the Heart Eater soul. With the Heart Eater soul, the MP return from the hearts you get for using Blood Sucker on furniture is more that the cost of casting, increasing both HP and MP.