"Drana commands me. I command my nulls. And so her bidding is done."

Drana's Chosen

Cohort — {T}, Tap an untapped Ally you control: Create a tapped 2/2 black Zombie creature token.

Oath of the Gatewatch

Cohort — {T}, Tap an untapped Ally you control: Put a 2/2 black Zombie creature token onto the battlefield tapped.

Oath of the Gatewatch Promos

To activate a cohort ability, the Ally with that ability must have been under your control continuously since the beginning of your most recent turn. Informally, it can’t have “summoning sickness.” However, the other Ally you tap can be one that just came under your control. (Note that tapping the second Ally doesn’t use {T} [the tap symbol].)