Kindred Discovery

Mana cost: {3}{U}{U}
Type: Enchantment
Set: Alchemy Horizons: Baldur's Gate #126 (rare)

As this enchantment enters, choose a creature type.
Whenever a creature you control of the chosen type enters or attacks, draw a card.

Kindred Discovery has 13 printings, first in Commander 2017 (2017). EDHREC ranks it #339 among Commander cards. It appears most in Hakbal of the Surging Soul decks (17,649 on EDHREC). 4 public decks on TCG run it. It has 4 official rulings.

Legality

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

Public decks that run Kindred Discovery

Avengers Assemble - Marvel Super Heroes, led by Captain America, Team Leader
Draconic Domination - Commander 2017, led by The Ur-Dragon
Everyone's Invited - Secret Lair Drop - WUBRG EDH Precon Decklist, led by Morophon, the Boundless
Explorers of the Deep - The Lost Caverns of Ixalan Commander, led by Hakbal of the Surging Soul

Commanders that run Kindred Discovery most

Deck counts from EDHREC.

Hakbal of the Surging Soul: 17,649 decks
The Ur-Dragon: 12,661 decks
Alela, Cunning Conqueror: 10,501 decks
Miirym, Sentinel Wyrm: 9,628 decks
Sidar Jabari of Zhalfir: 8,185 decks
The First Sliver: 7,432 decks
Alela, Artful Provocateur: 7,109 decks
Choco, Seeker of Paradise: 6,992 decks

Often played with Kindred Discovery

Cards that show up in the same decks on EDHREC.

Rulings

2017-08-25: If you somehow control a Kindred Discovery with no chosen creature type, its last ability can't trigger, even if a creature with no creature types enters the battlefield or attacks.
2022-06-10: You must choose an existing creature type, such as Human or Warrior. Card types such as artifact and supertypes such as legendary can't be chosen.
2022-06-10: The choice of creature type is made as Kindred Discovery enters the battlefield. Players can't take any actions between the time the choice is made and the time it enters the battlefield. Notably, this means that if it is entering the battlefield at the same time as any creatures of the chosen type, its last ability will trigger.
2023-09-01: You can't choose multiple creature types, such as "Cat Warrior." A Cat Warrior is both a Cat and a Warrior. It's affected by anything that affects either type and unaffected by things that affect non-Cat or non-Warrior creatures.