Sidisi, Thrall Caster

Deathtouch
Whenever you tap a swamp, amass 1.
Whenever a +1/+1 counter is placed on a zombie
you control, target opponent loses 1 life.
All zombies you control with 8 or more power
have swampwalk and infect.
{t}, sacrifice a zombie: untap {x} swamps, where {x} is equal to half that zombie's attack, rounded
down.