Consumptive Goo

{2}{B}{B}: Target creature gets -1/-1 until end of turn. Put a +1/+1 counter on Consumptive Goo.

Pestilence

At the beginning of the end step, if no creatures are on the battlefield, sacrifice Pestilence.
{B}: Pestilence deals 1 damage to each creature and each player.

Plague Witch

{B}, {T}, Discard a card: Target creature gets -1/-1 until end of turn.

Sol Ring

Cuombajj Witches

{T}: Cuombajj Witches deals 1 damage to any target and 1 damage to any target of an opponent's choice.

Abyssal Hunter

{B}, {T}: Tap target creature. Abyssal Hunter deals damage equal to Abyssal Hunter's power to that creature.

Torture Chamber

At the beginning of your upkeep, put a pain counter on Torture Chamber.
At the beginning of your end step, Torture Chamber deals damage to you equal to the number of pain counters on it.
{1}, {T}, Remove all pain counters from Torture Chamber: It deals damage to target creature equal to the number of pain counters removed this way.