Traxos, Scourge of Kroog

Mana cost: {4}
Type: Legendary Artifact Creature — Dragon Construct
Power / toughness: 7 / 7
Set: Dominaria United Commander #195 (rare)
Price: $0.40 USD

Trample
Traxos enters tapped and doesn't untap during your untap step.
Whenever you cast a historic spell, untap Traxos. (Artifacts, legendaries, and Sagas are historic.)

Traxos, Scourge of Kroog has 6 printings, first in Dominaria (2018). EDHREC ranks it #3,951 among Commander cards. It appears most in Aloy, Savior of Meridian decks (6,716 on EDHREC). 2 public decks on TCG run 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 Traxos, Scourge of Kroog

Legends' Legacy - Dominaria United, led by Dihada, Binder of Wills
Mishra's Burnished Banner - The Brothers' War Commander, led by Mishra, Eminent One

Commanders that run Traxos, Scourge of Kroog most

Deck counts from EDHREC.

Aloy, Savior of Meridian: 6,716 decks
Meria, Scholar of Antiquity: 2,060 decks
Abigale, Eloquent First-Year: 1,965 decks
Golbez, Crystal Collector: 1,926 decks
Dihada, Binder of Wills: 1,474 decks
Mishra, Eminent One: 911 decks
Mm'menon, the Right Hand: 544 decks
Lara Croft, Tomb Raider: 498 decks

Often played with Traxos, Scourge of Kroog

Cards that show up in the same decks on EDHREC.

Rulings

2018-04-27: Some abilities trigger "whenever you cast a historic spell." Such an ability resolves before the spell that caused it to trigger. It resolves even if that spell is countered.
2018-04-27: Lands are never cast, so abilities that trigger "whenever you cast a historic spell" won't trigger if you play a legendary land. They also won't trigger if a card on the battlefield transforms into a legendary land, as the Ixalan and Rivals of Ixalan double-faced cards do.
2018-04-27: A card, spell, or permanent is historic if it has the legendary supertype, the artifact card type, or the Saga subtype. Having two of those qualities doesn't make an object more historic than another or provide an additional bonus—an object either is historic or it isn't.
2018-04-27: An ability that triggers "whenever you cast a historic spell" doesn't trigger if a historic card is put onto the battlefield without being cast.