Call for Unity

Mana cost: {3}{W}{W}
Type: Enchantment
Set: Aether Revolt #9 (rare)
Price: $0.20 USD

Revolt — At the beginning of your end step, if a permanent left the battlefield under your control this turn, put a unity counter on this enchantment.
Creatures you control get +1/+1 for each unity counter on this enchantment.

Call for Unity has 3 printings, first in Aether Revolt (2017). EDHREC ranks it #8,399 among Commander cards. It appears most in Frodo, Adventurous Hobbit // Sam, Loyal Attendant decks (5,419 on EDHREC). 1 public deck on TCG runs it. It has 5 official rulings.

Legality

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

Public decks that run Call for Unity

Food and Fellowship - Tales of Middle-earth Commander, led by Sam, Loyal Attendant

Commanders that run Call for Unity most

Deck counts from EDHREC.

Frodo, Adventurous Hobbit // Sam, Loyal Attendant: 5,419 decks
Minthara, Merciless Soul: 1,810 decks
Syr Vondam, Sunstar Exemplar: 493 decks
Phelia, Exuberant Shepherd: 334 decks
Roon of the Hidden Realm: 247 decks
Genku, Future Shaper: 109 decks
Triad of Fates: 101 decks
Senu, Keen-Eyed Protector: 34 decks

Often played with Call for Unity

Cards that show up in the same decks on EDHREC.

Rulings

2017-02-09: All cards in the Aether Revolt set with triggered revolt abilities use an intervening "if" clause. A permanent you controlled must have left the battlefield earlier in the turn in order for these abilities to trigger; otherwise they do nothing. In other words, there's no way to have the ability trigger if no permanent you controlled has left the battlefield that turn, even if you intend to have one do so in response to the triggered ability.
2017-02-09: Revolt abilities check only whether a permanent you controlled left the battlefield this turn or not. They don't apply multiple times if more than one permanent you controlled left the battlefield. They don't check whether the permanent that left the battlefield is still in the zone it moved to.
2017-02-09: Energy counters aren't permanents. Paying {E} won't satisfy a revolt ability.
2017-02-09: Tokens that leave the battlefield will satisfy a revolt ability.
2017-02-09: Revolt abilities don't care why the permanent left the battlefield, who caused it to move, or where it moved to. They're equally satisfied by an artifact you sacrificed to pay a cost, a creature you controlled that was destroyed by Murder, or an enchantment you returned to your hand with Leave in the Dust.