Cryptborn Horror

Trample
This creature enters with X +1/+1 counters on it, where X is the total life lost by your opponents this turn.

Mountain

Phyrexian Arena

At the beginning of your upkeep, you draw a card and you lose 1 life.

Azra Oddsmaker

At the beginning of combat on your turn, you may discard a card. If you do, choose a creature. Whenever that creature deals combat damage to a player this turn, you draw two cards.

Falthis, Shadowcat Familiar

Commanders you control have menace and deathtouch.
Partner (You can have two commanders if both have partner.)

Jeska, Thrice Reborn

Jeska enters with a loyalty counter on her for each time you've cast a commander from the command zone this game.
0: Choose target creature. Until your next turn, if that creature would deal combat damage to one of your opponents, it deals triple that damage to that player instead.
−X: Jeska deals X damage to each of up to three targets.
Jeska, Thrice Reborn can be your commander.
Partner

Blood Pet

Serrated Scorpion

When this creature dies, it deals 2 damage to each opponent and you gain 2 life.

Kederekt Parasite

Whenever an opponent draws a card, if you control a red permanent, you may have this creature deal 1 damage to that player.

Mana Geyser

Add {R} for each tapped land your opponents control.

Underworld Dreams

Whenever an opponent draws a card, this enchantment deals 1 damage to that player.

Read the Bones

Scry 2, then draw two cards. You lose 2 life. (To scry 2, look at the top two cards of your library, then put any number of them on the bottom and the rest on top in any order.)

Dauthi Mercenary

Shadow (This creature can block or be blocked by only creatures with shadow.)
{1}{B}: This creature gets +1/+0 until end of turn.

Tectonic Hazard

Tectonic Hazard deals 1 damage to each opponent and each creature they control.

Iridescent Vinelasher

Offspring {2} (You may pay an additional {2} as you cast this spell. If you do, when this creature enters, create a 1/1 token copy of it.)
Landfall — Whenever a land you control enters, this creature deals 1 damage to target opponent.

Obosh, the Preypiercer

Companion — Your starting deck contains only cards with odd mana values and land cards. (If this card is your chosen companion, you may put it into your hand from outside the game for {3} as a sorcery.)
If a source you control with an odd mana value would deal damage to a permanent or player, it deals double that damage to that permanent or player instead.

Seething Song

Burnished Hart

{3}, Sacrifice this creature: Search your library for up to two basic land cards, put them onto the battlefield tapped, then shuffle.

Alloy Myr

Necropotence

Skip your draw step.
Whenever you discard a card, exile that card from your graveyard.
Pay 1 life: Exile the top card of your library face down. Put that card into your hand at the beginning of your next end step.

Dauthi Marauder

Shadow (This creature can block or be blocked by only creatures with shadow.)

Dark Ritual

Sol Ring

Pyrite Spellbomb

{R}, Sacrifice this artifact: It deals 2 damage to any target.
{1}, Sacrifice this artifact: Draw a card.

Dauthi Jackal

Shadow (This creature can block or be blocked by only creatures with shadow.)
{B}{B}, Sacrifice this creature: Destroy target blocking creature.

Commander's Sphere

{T}: Add one mana of any color in your commander's color identity.
Sacrifice this artifact: Draw a card.

Swamp

Boltwave

Boltwave deals 3 damage to each opponent.

End the Festivities

End the Festivities deals 1 damage to each opponent and each creature and planeswalker they control.

Necrologia

Cast this spell only during your end step.
As an additional cost to cast this spell, pay X life.
Draw X cards.

Sisters of the Flame

Lightning Bolt

Lightning Bolt deals 3 damage to any target.

Risk Factor

Target opponent may have Risk Factor deal 4 damage to them. If that player doesn't, you draw three cards.
Jump-start (You may cast this card from your graveyard by discarding a card in addition to paying its other costs. Then exile this card.)

Fire Covenant

As an additional cost to cast this spell, pay X life.
Fire Covenant deals X damage divided as you choose among any number of target creatures.

Browbeat

Any player may have Browbeat deal 5 damage to them. If no one does, target player draws three cards.

Wayfarer's Bauble

{2}, {T}, Sacrifice this artifact: Search your library for a basic land card, put that card onto the battlefield tapped, then shuffle.