Rage into the Valley
Sorcery
The Goblin army poured in, driving wildly between the arms of the Mountain, seeking for the foe.
Rulings (6)
Amass Orcs works the same way, except you create a 0/0 black Orc Army creature token if you don't control an Army. And if the Army creature you chose isn't already an Orc, it becomes an Orc in addition to its other types. By combining cards with amass Orcs and amass Goblins, you can end up with a Goblin Orc Army.
Some cards refer to the "amassed Army." That means the Army creature you chose to receive counters, even if no counters were placed on it for some reason.
To amass Goblins N, if you don't control an Army creature, create a 0/0 black Goblin Army creature token. Then you choose an Army creature you control and put N +1/+1 counters on it. If that Army isn't already a Goblin, it becomes a Goblin in addition to its other types.
Legality
Formats by platform