Enchant creature
Whenever enchanted creature deals damage to a player, return target creature that player controls to its owner's hand.

Add .

Choose an opponent. They look at the top four cards of your library and separate them into a face-down pile and a face-up pile. Put one pile into your hand and the other into your graveyard. The Ring tempts you.

Whenever another nontoken creature enters, you may pay . If you do, that creature's controller creates a token that's a copy of that creature.

Creatures you control have vigilance.
+1: You gain 3 life.
−2: Put a +1/+1 counter on each creature you control and a loyalty counter on each other planeswalker you control.

: Add .
: Add or . This land deals 1 damage to you.

When this creature enters, destroy target artifact or enchantment an opponent controls.

Return target creature to its owner's hand. Then return another target creature to its owner's hand unless its controller pays .

Commander creatures you own have "When this creature enters and at the beginning of your upkeep, each player may put two +1/+1 counters on a creature they control. For each opponent who does, you gain protection from that player until your next turn." (You can't be targeted, dealt damage, or enchanted by anything controlled by that player.)

Companion — Each nonland card in your starting deck has a different name. (If this card is your chosen companion, you may put it into your hand from outside the game for as a sorcery.)
Flash
When Lutri enters, if you cast it, copy target instant or sorcery spell you control. You may choose new targets for the copy.

Whenever this creature is dealt damage, you may create that many 1/1 green Insect creature tokens.
Morph (You may cast this card face down as a 2/2 creature for . Turn it face up any time for its morph cost.)

Each player discards their hand, then draws cards equal to the greatest number of cards a player discarded this way.

Sacrifice a creature: Draw cards equal to the sacrificed creature's power, then discard three cards.

At the beginning of each opponent's upkeep, this creature deals X damage to that player, where X is 3 minus the number of cards in their hand.

Whenever this creature or another Elemental you control enters, look at the top card of your library. If it's a land card, you may put it onto the battlefield tapped. If you don't put the card onto the battlefield, put it into your hand.

Flash
Synaptic Disintegrator — When this creature enters, destroy up to one target creature and target player mills three cards.

Bushido 1 (Whenever this creature blocks or becomes blocked, it gets +1/+1 until end of turn.)
Whenever a creature an opponent controls dies, you may cast target instant card from your graveyard. If that spell would be put into a graveyard, exile it instead.

Untap target creature and gain control of it until end of turn. That creature gains haste until end of turn. (It can attack and this turn.)

This creature gets +1/+1 for each creature card in your graveyard.
, , Sacrifice another creature: Search your library for a creature card with mana value X or less, put it onto the battlefield, then shuffle. Activate only as a sorcery.

At the beginning of your upkeep, each opponent loses X life and you scry X, where X is the number of Zombies you control.
: Exile target creature card from a graveyard. Create a token that's a copy of it, except it's a 4/4 black Zombie.
When The Scarab God dies, return it to its owner's hand at the beginning of the next end step.