Sandsteppe Outcast

When this creature enters, choose one —
• Put a +1/+1 counter on this creature.
• Create a 1/1 white Spirit creature token with flying.

Foundations Jumpstart

When Sandsteppe Outcast enters, choose one —
• Put a +1/+1 counter on Sandsteppe Outcast.
• Create a 1/1 white Spirit creature token with flying.

Jumpstart: Historic Horizons

Fate Reforged

When Sandsteppe Outcast enters the battlefield, choose one —
• Put a +1/+1 counter on Sandsteppe Outcast.
• Put a 1/1 white Spirit creature token with flying onto the battlefield.

If a mode requires a target and there are no legal targets available, that mode can't be chosen. You must choose another mode if able.

You choose which mode you're using as you put the ability on the stack, after the creature has entered the battlefield. Once you've chosen a mode, you can't change that mode even if the creature leaves the battlefield in response to that ability.