Terror of Mount Velus

Flying, double strike
When Terror of Mount Velus enters, creatures you control gain double strike until end of turn.

Snowfield Sinkhole

({T}: Add {W} or {B}.)
Snowfield Sinkhole enters tapped.

Rocky Tar Pit

Rocky Tar Pit enters tapped.
{T}, Sacrifice Rocky Tar Pit: Search your library for a Swamp or Mountain card, put it onto the battlefield, then shuffle.

Demon of Loathing

Flying, trample
Whenever Demon of Loathing deals combat damage to a player, that player sacrifices a creature.

Marsh Flats

{T}, Pay 1 life, Sacrifice Marsh Flats: Search your library for a Plains or Swamp card, put it onto the battlefield, then shuffle.

Harvester of Souls

Deathtouch
Whenever another nontoken creature dies, you may draw a card.

Sunlit Marsh

({T}: Add {W} or {B}.)
Sunlit Marsh enters tapped.

Rakdos Signet

Sacred Peaks

({T}: Add {R} or {W}.)
Sacred Peaks enters tapped.

Arid Mesa

{T}, Pay 1 life, Sacrifice Arid Mesa: Search your library for a Mountain or Plains card, put it onto the battlefield, then shuffle.

Savai Triome

({T}: Add {R}, {W}, or {B}.)
Savai Triome enters tapped.
Cycling {3} ({3}, Discard this card: Draw a card.)