Mutate (If you cast this spell for its mutate cost, put it over or under target non-Human creature you own. They mutate into the creature on top plus all abilities from under it.)

Flying

Whenever this creature mutates, draw a card.

Whenever you cast a Spirit or Arcane spell, you may put a ki counter on this creature.

, , Remove X ki counters from this creature: Return target creature with mana value X or less to its owner's hand.

Flying

Whenever Niv-Mizzet deals damage to a player, you may draw a card.

: Niv-Mizzet deals 1 damage to any target.

Flying

Whenever you draw a card, Niv-Mizzet deals 1 damage to any target.

: Draw a card.

Flying, lifelink

Spells you cast have delve. (Each card you exile from your graveyard while casting those spells pays for .)

Whenever you cast a spell, you lose life equal to its mana value.

Flying

Whenever you cast a noncreature spell, creatures you control get +1/+1 until end of turn.

Flying

Whenever you cast a noncreature spell, this creature gets +2/+2 until end of turn.

Ward

Whenever you cast your second spell each turn, amass Orcs 2. (Put two +1/+1 counters on an Army you control. It's also an Orc. If you don't control an Army, create a 0/0 black Orc Army creature token first.)

Whenever you cast a green spell, you may create a 2/2 green Wolf creature token.

Whenever you cast a blue spell, you may create a 1/1 blue Bird creature token with flying.

You may look at the top card of your library any time.

You may cast Spider spells and noncreature spells from the top of your library.

Whenever you attack, you may mill a card. (You may put the top card of your library into your graveyard.)

Whenever you cast an instant, sorcery, or Wizard spell, this creature gains flying until end of turn.

This spell can't be countered.

Flying

Whenever you draw a card, Niv-Mizzet deals 1 damage to any target.

Whenever a player casts an instant or sorcery spell, you draw a card.

Convoke (Your creatures can help cast this spell. Each creature you tap while casting this spell pays for or one mana of that creature's color.)

Flying, vigilance

Whenever this creature attacks, the next spell you cast this turn has convoke.

Flying

When this creature enters, you may search your library for a card with flashback or disturb, put it into your graveyard, then shuffle.

Flying

Whenever this creature becomes the target of a spell or ability for the first time each turn, counter that spell or ability.

Whenever you cast a spell, proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

Flying

Inspired — Whenever this creature becomes untapped, draw a card.

Whenever this creature enters or attacks, you may sacrifice an artifact. If you do, draw a card.