Helm of the Host

Mana cost: {4}
Type: Legendary Artifact — Equipment
Set: The Brothers' War Retro Artifacts #82z (mythic)

At the beginning of combat on your turn, create a token that's a copy of equipped creature, except the token isn't legendary. That token gains haste.
Equip {5}

Helm of the Host has 10 printings, first in Dominaria (2018). EDHREC ranks it #392 among Commander cards. It appears most in Deadpool, Trading Card decks (12,023 on EDHREC). 2 public decks on TCG run it. It has 8 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 Helm of the Host

Family Matters - Bloomburrow Commander, led by Zinnia, Valley's Voice
Wakanda Forever - Marvel Super Heroes, led by T'Challa, the Black Panther

Commanders that run Helm of the Host most

Deck counts from EDHREC.

Deadpool, Trading Card: 12,023 decks
Kaalia of the Vast: 7,535 decks
Cloud, Ex-SOLDIER: 6,006 decks
Isshin, Two Heavens as One: 5,466 decks
Roxanne, Starfall Savant: 5,269 decks
Zinnia, Valley's Voice: 4,860 decks
T'Challa, the Black Panther: 3,828 decks
Etali, Primal Conqueror // Etali, Primal Sickness: 3,791 decks

Often played with Helm of the Host

Cards that show up in the same decks on EDHREC.

Rulings

2018-04-27: Any enters-the-battlefield abilities of the copied creature will trigger when the token enters the battlefield. Any "as [this creature] enters the battlefield" or "[this creature] enters the battlefield with" abilities of the chosen creature will also work.
2018-04-27: If the equipped creature leaves the battlefield before the triggered ability of Helm of the Host resolves, or if there is no equipped creature, no token is created. However, if Helm of the Host leaves the battlefield while its triggered ability is on the stack, a token will be created of the creature it last equipped. If that creature has also left the battlefield, its last known information is used to determine what the token looks like.
2018-04-27: If the copied creature has {X} in its mana cost, X is considered to be 0.
2018-04-27: The token isn't legendary, and this exception is copiable. If something else copies the token later, that copy also won't be legendary. If you control two or more permanents with the same name but only one is legendary, the "legend rule" doesn't apply.
2018-04-27: If the copied creature is copying something else (for example, if the copied creature is a Clone), then the token enters the battlefield as whatever that creature copied.
2018-04-27: The token copies exactly what was printed on the original creature and nothing else (unless that creature is copying something else or is a token; see below). It doesn't copy whether that creature is tapped or untapped, whether it has any counters on it or Auras and Equipment attached to it, or any non-copy effects that have changed its power, toughness, types, color, and so on.
2018-04-27: The token gains haste indefinitely, and this effect isn't copiable. If something else copies the token later, that copy won't have haste.
2018-04-27: If the copied creature is a token, the token that's created copies the original characteristics of that token as stated by the effect that created that token.