Nezahal, Primal Tide

Mana cost: {5}{U}{U}
Type: Legendary Creature — Elder Dinosaur
Power / toughness: 7 / 7
Set: Rivals of Ixalan Promos #45s (rare)

This spell can't be countered.
You have no maximum hand size.
Whenever an opponent casts a noncreature spell, draw a card.
Discard three cards: Exile Nezahal. Return it to the battlefield tapped under its owner's control at the beginning of the next end step.

Nezahal, Primal Tide has 8 printings, first in Rivals of Ixalan (2018). EDHREC ranks it #1,131 among Commander cards. It appears most in Kinnan, Bonder Prodigy decks (13,077 on EDHREC). 1 public deck on TCG runs 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 Nezahal, Primal Tide

Reap the Tides - Commander Legends, led by Aesi, Tyrant of Gyre Strait

Commanders that run Nezahal, Primal Tide most

Deck counts from EDHREC.

Kinnan, Bonder Prodigy: 13,077 decks
Hashaton, Scarab's Fist: 12,574 decks
Aesi, Tyrant of Gyre Strait: 5,934 decks
Marvo, Deep Operative: 4,457 decks
Satoru Umezawa: 3,843 decks
Owen Grady, Raptor Trainer // Blue, Loyal Raptor: 3,661 decks
Mr. Foxglove: 2,818 decks
Braids, Conjurer Adept: 2,809 decks

Often played with Nezahal, Primal Tide

Cards that show up in the same decks on EDHREC.

Rulings

2018-01-19: Nezahal's triggered ability resolves before the noncreature spell that caused it to trigger.
2018-01-19: Players can cast spells and activate abilities after Nezahal's 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 or may be discarded to activate Nezahal's last ability.
2018-01-19: Your maximum hand size is checked only during the cleanup step on your turn. If Nezahal's last ability is activated before your turn's end step, it will return before your next cleanup step and you'll have no maximum hand size.
2018-01-19: After Nezahal returns to the battlefield, it will be a new object with no connection to the creature that was exiled. It won't be in combat or have any additional abilities it may have had when it was exiled. Any +1/+1 counters on it or Auras attached to it are removed, and any Equipment will no longer be attached.