If you don't control an Army, the Zombie Army token you create enters the battlefield as a 0/0 creature before receiving counters. Any abilities that trigger when a creature with a certain power enters the battlefield, such as that of Mentor of the Meek, will see the token enter as a 0/0 creature before it gets +1/+1 counters.
Toll of the Invasion
In the rare case that you control multiple Army creatures (perhaps because you played a creature with changeling) while you amass Zombies, you choose which of your Army creatures to put the +1/+1 counters on. If that creature isn't a Zombie, it becomes a Zombie in addition to its other types.
Some spells and abilities that amass Zombies may require targets. If each target chosen is an illegal target as that spell or ability tries to resolve, it won't resolve. You won't amass Zombies.
Magic: The Gathering · ™ & © Wizards of the Coast · Illus. Joe Slucher
Card data via Scryfall. Rarix is fan-made; not endorsed by the rights holders.
