This spell is a part of the Psy Dagger spell chain and is found in the Psy Dagger rune stone.
The mind is, among other things, a sequence. One thought leading to the next, one action giving way to another, time moving forward through the simple act of deciding what comes next. Nightmare finds this sequence and breaks it - not by destroying what came before, but by removing what comes after.
Mind Trap reaches through Nightmare and locks the target's mind onto the last action it completed before the spell landed, and holds it there. The loop is immediate and total. The target cannot advance past that moment. Whatever they did - drew a weapon, reached for a potion, took a step, swung at an enemy - that is what they will do again. And again. And again, for the duration, because their mind cannot find the next thought. It keeps returning to the last one it had, convinced that this is still the moment, that this is still what needs doing, that time has not moved at all. The target reaches for a potion that is no longer there. They swing at an enemy that has stepped away. They move in a direction they have already moved. Nightmare does not care about the logic of it. It only holds the loop and watches the target run it, round after round, until the spell's duration ends and the sequence finally, mercifully, resumes.
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