When casted on a group of people it puts them into a nightmare unless they make a saving throw against the caster spell DC, they wake before being attacked (they can react but take no action). It lasts for 1 round but feels like they have been in there longer. The character is still standing when trapped in a nightmare but can’t move, cast a spell, see or hear, or anything like that, but can talk. The caster knows what's going on inside the nightmare so the player will have to explain the character's worst nightmares.