This spell is a part of the Fang spell chain and is found in the Fang rune stone.
Pain does not always want to finish things. That is perhaps the most important distinction between Pain and death. Death wants resolution, wants the ending, wants the peace that comes after. Pain wants none of those things. Pain wants continuation. It wants the experience to go on, wants every moment to be fully felt, wants to ensure that nothing about what it is doing gets to stop before Pain has decided it is finished. Pain's Persistence is that desire made into a spell.
When the necromancer casts this spell they reach into Pain and ask it not to kill, overwhelm, or break, but simply to persist. To take hold of the target's body and fill it so completely with its presence that the target can do almost nothing without that presence making itself known. Pain obliges with something approaching enthusiasm, settling into the target's body like a weight that cannot be shifted, a constant ache that flares into agony the moment the target attempts anything that requires real effort or commitment. For the duration the target cannot bring themselves to swing a weapon or loose an arrow as the movement required is simply too much with Pain flaring white-hot at every attempt. They are reduced to only the simplest of spells, those requiring no more than 1 runic speed, as well as only the most basic of skills, nothing beyond tier level 1. They are not helpless. They are simply made to understand, with great thoroughness, what it feels like to exist inside a body that Pain has decided to occupy fully. The necromancer feels this casting in their own body afterward. They experience a dull persistent ache settling into their joints and hands that lasts for 1d4 rounds, Pain's reminder that persistence cuts both ways.
Weapon Effect: Pain's Persistence
Critical Hit stuns target for 1 round