Is Guardian Scalelord legal in Standard, Modern, and Commander?

Guardian Scalelord is legal in: Legacy, Vintage, Commander.

Guardian Scalelord

Q: What type of card is Guardian Scalelord?

Guardian Scalelord is a Creature — Dragon. Its oracle text reads: "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.) Flying Whenever this creature attacks, return target nonland permanent card with mana value X or less from your graveyard to the battlefield, where X is this creature's power."

Creature — Dragon

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.)

Flying

Whenever this creature attacks, return target nonland permanent card with mana value X or less from your graveyard to the battlefield, where X is this creature's power.

Set March of the Machine Commander

Rarity Rare

Mana Value 5

Artist Victor Adame Minguez

Collector # 16

Scryfall Gatherer