"Where did I find my horned friend? Now there's a story worth telling. . . ."

Maestros Diabolist

Deathtouch, haste
Whenever this creature attacks, if you don't control a Devil token, create a tapped and attacking 1/1 red Devil creature token with "When this token dies, it deals 1 damage to any target."

Streets of New Capenna Promos

Streets of New Capenna

Deathtouch, haste
Whenever Maestros Diabolist attacks, if you don't control a Devil token, create a tapped and attacking 1/1 red Devil creature token with "When this creature dies, it deals 1 damage to any target."

Maestros Diabolist's triggered ability has an "intervening 'if'" clause. This means that it checks to see if you control a Devil token both when the ability triggers and when it resolves. Notably, this means that attacking with two Maestros Diabolists will normally cause you to create only one Devil token.

Devil

When this creature dies, it deals 1 damage to any target.