Whenever you cast an instant or sorcery spell, you may pay . If you do, copy that spell. You may choose new targets for the copy.
Whenever another nontoken creature enters the battlefield under your control, you may pay . If you do, create a token that's a copy of that creature.

Whenever you cast a Dog spell, create a 1/1 green Cat creature token.
Whenever you cast a Cat spell, create a 1/1 white Dog creature token.
, : Rin and Seri, Inseparable deals damage to any target equal to the number of Dogs you control. You gain life equal to the number of Cats you control.

Ring of Three Wishes enters the battlefield with three wish counters on it.
, , Remove a wish counter from Ring of Three Wishes: Search your library for a card and put that card into your hand. Then shuffle your library.

Put all creature cards from all graveyards onto the battlefield under your control.

Risen Executioner can't block.
Other Zombie creatures you control get +1/+1.
You may cast Risen Executioner from your graveyard if you pay more to cast it for each other creature card in your graveyard.

Flying, trample
When Roalesk, Apex Hybrid enters the battlefield, put two +1/+1 counters on another target creature you control.
When Roalesk dies, proliferate, then proliferate again. (Choose any number of permanents and/or players, then give each another counter of each kind already there. Then do it again.)

Reach, haste
Whenever Robber of the Rich attacks, if defending player has more cards in hand than you, exile the top card of their library. During any turn you attacked with a Rogue, you may cast that card and you may spend mana as though it were mana of any color to cast that spell.

Whenever you cast a spell, put a 0/1 colorless Egg artifact creature token onto the battlefield.
Whenever an Egg you control is put into a graveyard from the battlefield, destroy target artifact or creature.

Vigilance, trample
, : Exile another target creature. Return that card to the battlefield under its owner's control at the beginning of the next end step.

Menace
When Rot Hulk enters the battlefield, return up to X target Zombie cards from your graveyard to the battlefield, where X is the number of opponents you have.

[+2]: During target player's next turn, each creature that player controls attacks if able.
[−2]: Rowan Kenrith deals 3 damage to each tapped creature target player controls.
[−8]: Target player gets an emblem with "Whenever you activate an ability that isn't a mana ability, copy it. You may choose new targets for the copy."
Partner with Will Kenrith
Rowan Kenrith can be your commander.

[+1]: Up to one target creature gets +3/+0 and gains first strike until end of turn.
[−2]: Rowan, Fearless Sparkmage deals 1 damage to each of up to two target creatures. Those creatures can't block this turn.
[−9]: Gain control of all creatures until end of turn. Untap them. They gain haste until end of turn.

Trample
When Rowdy Crew enters the battlefield, draw three cards, then discard two cards at random. If two cards that share a card type are discarded this way, put two +1/+1 counters on Rowdy Crew.

At the beginning of combat on your turn, choose an opponent at random. Ruhan of the Fomori attacks that player this combat if able.

Heroic — Whenever you cast a spell that targets Sage of Hours, put a +1/+1 counter on it.
Remove all +1/+1 counters from Sage of Hours: For each five counters removed this way, take an extra turn after this one.

[+1]: Scry 1. Saheeli Rai deals 1 damage to each opponent.
[−2]: Create a token that's a copy of target artifact or creature you control, except it's an artifact in addition to its other types. That token gains haste. Exile it at the beginning of the next end step.
[−7]: Search your library for up to three artifact cards with different names, put them onto the battlefield, then shuffle your library.

[+1]: Create a 1/1 colorless Servo artifact creature token.
[+1]: The next spell you cast this turn costs less to cast for each artifact you control as you cast it.
[−7]: For each artifact you control, create a token that's a copy of it. Those tokens gain haste. Exile those tokens at the beginning of the next end step.
Saheeli, the Gifted can be your commander.

You may have Sakashima of a Thousand Faces enter the battlefield as a copy of another creature you control, except it has Sakashima of a Thousand Faces's other abilities.
The "legend rule" doesn't apply to permanents you control.
Partner (You can have two commanders if both have partner.)

Flash
Double strike, vigilance, haste
Other creatures you control have haste.
, : Untap another target creature.

[+1]: Up to one target creature gains double strike until end of turn.
[−2]: Samut, the Tested deals 2 damage divided as you choose among one or two targets.
[−7]: Search your library for up to two creature and/or planeswalker cards, put them onto the battlefield, then shuffle your library.