Arco-Flagellant

Squad {2} (As an additional cost to cast this spell, you may pay {2} any number of times. When this creature enters, create that many tokens that are copies of it.)
This creature can't block.
Endurant — Pay 3 life: This creature gains indestructible until end of turn.

Warhammer 40,000 Commander

Squad {2} (As an additional cost to cast this spell, you may pay {2} any number of times. When this creature enters the battlefield, create that many tokens that are copies of it.)
Arco-Flagellant can't block.
Endurant — Pay 3 life: Arco-Flagellant gains indestructible until end of turn.

Warhammer 40,000 Commander Tokens

Arco-Flagellant can't block.
Pay 3 life: Arco-Flagellant gains indestructible until end of turn.

If the spell is countered, the squad ability will not trigger, and no tokens will be created.

If, for some reason, the creature doesn't have the squad ability when it's on the battlefield, the ability won't trigger, even if you've paid the squad cost one or more times.

The tokens created by the squad ability aren't "cast," so any abilities that trigger when a spell is cast won't trigger for the copies.

You may pay the squad cost any number of times. You will get a token that is a copy of that permanent for each time you paid the squad cost.