Niv-Mizzet, Parun

Mana cost: {U}{U}{U}{R}{R}{R}
Type: Legendary Creature — Dragon Wizard
Power / toughness: 5 / 5
Set: Commander Legends: Battle for Baldur's Gate #851 (rare)
Price: $5.37 USD

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.

Niv-Mizzet, Parun has 11 printings, first in Guilds of Ravnica (2018). EDHREC ranks it #810 among Commander cards. It appears most in Vivi Ornitier decks (18,861 on EDHREC). 3 public decks on TCG run it. It has 4 official rulings.

Legality

commander: legal
legacy: legal
vintage: legal
pauper: not legal
modern: legal
pioneer: legal
standard: not legal
brawl: legal

Public decks that run Niv-Mizzet, Parun

Draconic Dissent - Commander Legends: Battle for Baldur's Gate, led by Firkraag, Cunning Instigator
Heads I Win, Tails You Lose - Secret Lair Drop, led by Zndrsplt, Eye of Wisdom
Quick Draw - Outlaws of Thunder Junction Commander, led by Stella Lee, Wild Card

Commanders that run Niv-Mizzet, Parun most

Deck counts from EDHREC.

Vivi Ornitier: 18,861 decks
Ghyrson Starn, Kelermorph: 13,351 decks
Kefka, Court Mage // Kefka, Ruler of Ruin: 9,682 decks
Nekusar, the Mindrazer: 6,547 decks
Niv-Mizzet, Visionary: 5,169 decks
Veyran, Voice of Duality: 5,142 decks
Stella Lee, Wild Card: 4,871 decks
Okaun, Eye of Chaos // Zndrsplt, Eye of Wisdom: 4,365 decks

Often played with Niv-Mizzet, Parun

Cards that show up in the same decks on EDHREC.

Rulings

2018-10-05: Players can cast spells and activate abilities after Niv-Mizzet's second triggered ability resolves but before the spell that caused it to trigger does. Notably, the card you draw may be able to counter that spell.
2018-10-05: If a spell or ability causes you to put cards into your hand without specifically using the word "draw," Niv-Mizzet's first triggered ability won't trigger.
2018-10-05: If an effect instructs you to draw multiple cards, Niv-Mizzet's first triggered ability triggers that many times. You choose targets for those abilities after you've drawn all of the cards.
2018-10-05: Niv-Mizzet's second triggered ability resolves before the spell that caused it to trigger. It resolves even if that spell is countered. This causes its first triggered ability to trigger, and that also resolves before the spell.