Have

Body Dropper

Whenever you sacrifice another creature, put a +1/+1 counter on Body Dropper.
{B}{R}, Sacrifice another creature: Body Dropper gains menace until end of turn. (It can't be blocked except by two or more creatures.)

Swamp

Altar's Reap

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

Assault Strobe

Target creature gains double strike until end of turn. (It deals both first-strike and regular combat damage.)

Myr Scrapling

Sacrifice Myr Scrapling: Put a +1/+1 counter on target creature.

Blood Pet

Terminate

Destroy target creature. It can't be regenerated.

Mountain

Lightning Bolt

Lightning Bolt deals 3 damage to any target.

Unearth

Return target creature card with mana value 3 or less from your graveyard to the battlefield.
Cycling {2} ({2}, Discard this card: Draw a card.)

Mortician Beetle

Whenever a player sacrifices a creature, you may put a +1/+1 counter on Mortician Beetle.

Aphotic Wisps

Target creature becomes black and gains fear until end of turn. (It can't be blocked except by artifact creatures and/or black creatures.)
Draw a card.