There are certain restrictions that can prevent you from placing a creature in a Sanctuary. The first major one being you cannot place more than 4 creatures in total across all your Sanctuaries (you can either place all 4 in one or spread them across 4 separate Sanctuaries.)

The following creatures cannot be placed:

- Creatures that are on your Strike Team.
- Hybrid creatures.
- Creatures that you already placed in another Sanctuary (creatures can’t be in two places at once!).
- Creatures that are too dangerous for your current Player Level, as shown on their creature card.