Is Conclave Sledge-Captain legal in Standard, Modern, and Commander?

Conclave Sledge-Captain is legal in: Legacy, Vintage, Commander.

Conclave Sledge-Captain

Q: What type of card is Conclave Sledge-Captain?

Conclave Sledge-Captain is a Creature — Elephant Soldier. Its oracle text reads: "Backup 1, backup 1, backup 1 (When this creature enters, put a +1/+1 counter on target creature. If that's another creature, it gains the following abilities until end of turn. Each backup ability triggers separately.) Trample Whenever this creature deals combat damage to a player, put that many +1/+1 counters on it."

Creature — Elephant Soldier

Backup 1, backup 1, backup 1 (When this creature enters, put a +1/+1 counter on target creature. If that's another creature, it gains the following abilities until end of turn. Each backup ability triggers separately.)

Trample

Whenever this creature deals combat damage to a player, put that many +1/+1 counters on it.

Set March of the Machine Commander

Rarity Rare

Mana Value 6

Artist Ilse Gort

Collector # 36

Scryfall Gatherer