Pestilence

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

Moseo, Vein's New Dean

Flying
When Moseo enters, create a 1/1 black and green Pest creature token with "Whenever this token attacks, you gain 1 life."
Infusion — At the beginning of your end step, if you gained life this turn, return up to one target creature card with mana value X or less from your graveyard to the battlefield, where X is the amount of life you gained this turn.

Pox Plague

Each player loses half their life, then discards half the cards in their hand, then sacrifices half the permanents they control of their choice. Round down each time.

Pestilence Demon

Flying
{B}: This creature deals 1 damage to each creature and each player.

Blight Mound

Attacking Pests you control get +1/+0 and have menace.
Whenever a nontoken creature you control dies, create a 1/1 black and green Pest creature token with "When this token dies, you gain 1 life."

Altar's Reap

As an additional cost to cast this spell, sacrifice a creature.
Draw two cards.

Decorum Dissertation

Target player draws two cards and loses 2 life.
Paradigm (Then exile this spell. After you first resolve a spell with this name, you may cast a copy of it from exile without paying its mana cost at the beginning of each of your first main phases.)