I would like to craft up some cleansing runes so I can carve my way through the Emprise du Lion. This requires corpse hearts, which apparently drop from possessed corpses. However, after murdering close to fifty corpse archers woken from the ponds of the Fallow Mire, I have yet to find a single heart.
Are corpse hearts really so rare, and I should just keep "fishing" in the Fallow Mire? Or do I need to find a different... kind... of corpse? Where can I obtain corpse hearts?
Preference will be given to answers that (a) don't depend on certain missions not being completed eg. Still Waters in Crestwood and (b) don't require DLC, since I'm on the XBox 360.