Alliance — Whenever another creature you control enters, choose one that hasn't been chosen this turn —
• Put a +1/+1 counter on this creature.
• Create a tapped Treasure token.
• You gain 2 life.

At the beginning of each opponent's upkeep, this artifact deals 2 damage to that player unless they have exactly three or exactly four cards in hand.

Equipped creature gets +10/+10 and loses flying.
Equip (: Attach to target creature you control. Equip only as a sorcery.)

Enrage — Whenever this creature is dealt damage, each opponent sacrifices a permanent of their choice.

Sliver creatures you control have deathtouch. (Any amount of damage a creature with deathtouch deals to a creature is enough to destroy it.)

If you control two or more other lands, this land enters tapped.
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: This land becomes a 3/4 white Dragon creature with flying until end of turn. It's still a land.

Exile target creature. Its controller may search their library for a basic land card, put that card onto the battlefield tapped, then shuffle.

Whenever an opponent casts a spell, that player loses 5 life unless they discard a card.

At the beginning of each player's end step, that player draws a card. If the player is your opponent and has four or more cards in hand, this enchantment deals 2 damage to that player.

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: This land deals 1 damage to target attacking creature. Activate only during the end of combat step.

Deathtouch
Whenever another creature you control enters, you gain 1 life.

Return all nonland permanents to their owners' hands. If you return four or more nontoken permanents you control this way, you may put a permanent card from your hand onto the battlefield.

Flying, hexproof from multicolored
Whenever Niv-Mizzet deals combat damage to a player, it deals X damage to any target, target player draws X cards, and you gain X life, where X is the number of different color pairs among permanents you control that are exactly two colors.

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When Toph enters, you may discard a card. If you do, return target instant or sorcery card from your graveyard to your hand.
Whenever you cast a spell, earthbend 1. If that spell is a Lesson, put an additional +1/+1 counter on that land. (Target land you control becomes a 0/0 creature with haste that's still a land. Put a +1/+1 counter on it. When it dies or is exiled, return it to the battlefield tapped.)

Vigilance, trample, lifelink
Once during each of your turns, you may cast an Aura or Equipment spell from your graveyard.

When this creature enters, return target creature card from your graveyard to the battlefield. You lose life equal to that card's mana value.

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Artifacts, creatures, and lands your opponents control enter tapped.

Flying
Lifelink (Damage dealt by this creature also causes you to gain that much life.)
Pegasus creatures you control have lifelink.
Constellation — Whenever an enchantment you control enters, create a 2/2 white Pegasus creature token with flying.