Unbreakable Formation

Mana cost: {2}{W}
Type: Instant
Set: Ravnica Allegiance Promos #29p (rare)
Price: $1.51 USD

Creatures you control gain indestructible until end of turn.
Addendum — If you cast this spell during your main phase, put a +1/+1 counter on each of those creatures and they gain vigilance until end of turn.

Unbreakable Formation has 16 printings, first in Ravnica Allegiance (2019). EDHREC ranks it #572 among Commander cards. It appears most in Éowyn, Shieldmaiden decks (9,806 on EDHREC). 8 public decks on TCG run it. It has 3 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 Unbreakable Formation

Arm for Battle - Commander Legends, led by Wyleth, Soul of Steel
Bangarang!, led by Derevi, Empyrial Tactician
Cavalry Charge - March of the Machine Commander, led by Sidar Jabari of Zhalfir
Coven Counters - Midnight Hunt Commander, led by Leinore, Autumn Sovereign
Legends' Legacy - Dominaria United, led by Dihada, Binder of Wills
Party Time - Commander Legends: Battle for Baldur's Gate, led by Nalia de'Arnise
Riders of Rohan - Tales of Middle-earth Commander, led by Éowyn, Shieldmaiden
Urza's Iron Alliance - The Brothers' War Commander, led by Urza, Chief Artificer

Commanders that run Unbreakable Formation most

Deck counts from EDHREC.

Often played with Unbreakable Formation

Cards that show up in the same decks on EDHREC.

Rulings

2019-01-25: Unbreakable Formation affects only creatures you control at the time it resolves. Creatures you begin to control later in the turn won't gain indestructible or vigilance and they won't get a +1/+1 counter.
2024-01-12: If an effect copies a spell with an addendum ability while it's on the stack, the copy wasn't cast at all, so you won't get the addendum bonus.
2024-01-12: Addendum abilities of instant spells apply while the spell is resolving, not immediately after casting it. If the spell is countered, you don't get the addendum bonus.