A player may purchase a Neutral Monster's Loyalty Card during the Doom Phase. A player may never purchase more than one of these in a given Doom Phase, but there is no limit to the number of Neutral Monster Loyalty Cards a player may possess.
To purchase one of these Loyalty Cards, pay 2 Doom when it is your turn to perform a Ritual of Annihilation. If you wish, you may still perform the Ritual. When spending Doom, choose a Neutral Monster Loyalty Card from among those available, placing that card and its associated monsters by your Faction Card. You will typically have the opportunity to immediately place one of these new Monsters for free.
Once you have purchased a Neutral Monster Loyalty Card, it is yours for the rest of the game. From then on, only you may summon and Control its associated Neutral Monsters.