Environ is a role for Challenges in exploration scenarios. Environs cannot Move and typically cannot be seen from adjacent unblocked regions, but the DM or scenario design may specify exceptions to this.
Environs act at the beginning of the round, and their Actions always target all PCs in their occupied region (unless otherwise specified). Scenario design will specify if an Environ is also able to target certain other Challenges. Some Environs occupy multiple regions and thus can target PCs in all occupied regions on each turn.