Unifying Theory

Whenever a player casts a spell, that player may pay {2}. If the player does, they draw a card.

Infantry Veteran

{T}: Target attacking creature gets +1/+1 until end of turn.

Loathsome Troll

{3}{G}: Roll a d20. Activate only if Loathsome Troll is in your graveyard.
1—9 | Put Loathsome Troll on top of your library.
10—19 | Return Loathsome Troll to your hand.
20 | Return Loathsome Troll to the battlefield tapped.

Black Lotus

{T}, Sacrifice Black Lotus: Add three mana of any one color.

Vampire Aristocrat

Sacrifice a creature: Vampire Aristocrat gets +2/+2 until end of turn.

Emergent Growth

Target creature gets +5/+5 until end of turn and must be blocked this turn if able.

Samite Alchemist

{W}{W}, {T}: Prevent the next 4 damage that would be dealt this turn to target creature you control. Tap that creature. It doesn't untap during your next untap step.

Oath of Ajani

When Oath of Ajani enters, put a +1/+1 counter on each creature you control.
Planeswalker spells you cast cost {1} less to cast.

Young Pyromancer

Whenever you cast an instant or sorcery spell, create a 1/1 red Elemental creature token.

Ob Nixilis of the Black Oath

+2: Each opponent loses 1 life. You gain life equal to the life lost this way.
−2: Create a 5/5 black Demon creature token with flying. You lose 2 life.
−8: You get an emblem with "{1}{B}, Sacrifice a creature: You gain X life and draw X cards, where X is the sacrificed creature's power."
Ob Nixilis of the Black Oath can be your commander.