With the right head of the Runespoor focused on the dog that you created and the middle and left heads still both under your previous spells there was just enough time to conjure firewood.

Carving thurisaz into the wood and chanting as you had worked just as you planned. The rune you created was indeed glowing as you held onto the wood tightly.

All the focus you put into creating that rune must have caused you to lose focus on that jelly brain jinx which was enough for the Runespoor to begin charging at you, dragging the middle head along.

The heads move aside just a second before it could have been hit with Deprimo. It charges at you again hissing even louder, fangs bared.

Perhaps using Runes and Charms isn't the best idea to subdue this Runespoor in nature.