Mr. Orfeo, the Boulder

Whenever you attack, double target creature's power until end of turn.

Feldon of the Third Path

{2}{R}, {T}: Create a token that's a copy of target creature card in your graveyard, except it's an artifact in addition to its other types. It gains haste. Sacrifice it at the beginning of the next end step.

Ghalta, Primal Hunger

This spell costs {X} less to cast, where X is the total power of creatures you control.
Trample

Phytotitan

When Phytotitan dies, return it to the battlefield tapped under its owner's control at the beginning of their next upkeep.

Gadrak, the Crown-Scourge

Flying
Gadrak, the Crown-Scourge can't attack unless you control four or more artifacts.
At the beginning of your end step, create a Treasure token for each nontoken creature that died this turn. (It's an artifact with "{T}, Sacrifice this artifact: Add one mana of any color.")

Arcane Signet

{T}: Add one mana of any color in your commander's color identity.

Jaxis, the Troublemaker

{R}, {T}, Discard a card: Create a token that's a copy of another target creature you control. It gains haste and "When this creature dies, draw a card." Sacrifice it at the beginning of the next end step. Activate only as a sorcery.
Blitz {1}{R} (If you cast this spell for its blitz cost, it gains haste and "When this creature dies, draw a card." Sacrifice it at the beginning of the next end step.)

Ayara, Furnace Queen

At the beginning of combat on your turn, return up to one target artifact or creature card from your graveyard to the battlefield. It gains haste. Exile it at the beginning of the next end step.

Ayara, Widow of the Realm

{T}, Sacrifice another creature or artifact: Ayara, Widow of the Realm deals X damage to target opponent or battle and you gain X life, where X is the sacrificed permanent's mana value.
{5}{R/P}: Transform Ayara. Activate only as a sorcery. ({R/P} can be paid with either {R} or 2 life.)

Ayara, Widow of the Realm // Ayara, Furnace Queen

Commander's Sphere

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

Yargle and Multani

Kalain, Reclusive Painter

When Kalain, Reclusive Painter enters, create a Treasure token. (It's an artifact with "{T}, Sacrifice this artifact: Add one mana of any color.")
Other creatures you control enter with an additional +1/+1 counter on them for each mana from a Treasure spent to cast them.

Rivaz of the Claw

Menace
{T}: Add two mana in any combination of colors. Spend this mana only to cast Dragon creature spells.
Once during each of your turns, you may cast a Dragon creature spell from your graveyard.
Whenever you cast a Dragon creature spell from your graveyard, it gains "When this creature dies, exile it."

Reckless Fireweaver

Whenever an artifact you control enters, Reckless Fireweaver deals 1 damage to each opponent.

Dragonmaster Outcast

At the beginning of your upkeep, if you control six or more lands, create a 5/5 red Dragon creature token with flying.

Marionette Master

Fabricate 3 (When this creature enters, put three +1/+1 counters on it or create three 1/1 colorless Servo artifact creature tokens.)
Whenever an artifact you control is put into a graveyard from the battlefield, target opponent loses life equal to Marionette Master's power.

Stalking Vengeance

Haste
Whenever another creature you control dies, it deals damage equal to its power to target player or planeswalker.

Unleash Fury

Double the power of target creature until end of turn.

Kresh the Bloodbraided

Whenever another creature dies, you may put X +1/+1 counters on Kresh the Bloodbraided, where X is that creature's power.

Sol Ring

Riveteers Ascendancy

Whenever you sacrifice a creature, you may return target creature card with lesser mana value from your graveyard to the battlefield tapped. Do this only once each turn.