(This is the same for Ash Piles, Ghostly Remains & Ice Wraith Remains) Make sure an ENEMY activates the rune and NOT a civilian. The game has to tack where you cast these spells and they can build up.
You can effectively speed up this process by 'Fast-Travelling' everywhere. You can also use this method for clearing old dungeons of 'glitchy' items such as weapons and loose loot that won't 're spawn.' Eventually, these items will disappear from your save file after just a few in-game days, weeks or even months when the enemies/containers re spawn. Dump any hoarded items from your house/s and some accumulating items that you give to followers in 're spawning items' such as: dead bandit bodies, giant's corpses or a container that you don't own.Unfavourite 'favourite' items that you've left in chests and given to followers.
