This is a life-draining, negative material explosion.

Innate Attack (Toxic) 2d [16] 
    Explosion 1 [+50%] 
    Triggered Delay [+50%] 
        Living being touching the skull 
        Damaging the skull 
    Malediction (As Regular Spell) [+100%] 
    Based on Activation Roll [+5%] 
    May Only be Planted on Non-Living Skulls [-60%] 
    Magical [-10%] 
    Spell Components [-30%] 
        Must say "skull" in Latin 
        Must gesture with hands 
        Must hold dust/ash from the remains of a vampire 
Levels 2-4 [24/32/39] 
    Increase damage by 1d [+4 base] 
Levels 5+ [+7.8/level 
    Increase damage by 1d [+4 base]