Pipers are a unique enemy in that they pursue Kain but they themselves do not pose a threat to him. Instead, they summon zombies that pose the immediate threat to Kain. They are first encountered in Nupraptor's retreat, but only one is ever encountered here. However, they are seen again in Corhagen where the plague has decimated the population of Kain's home village.
Thankfully, they are no tougher than brigands and can be stunned with the mace and fed from, at which point they will drop to the ground and die. Unfortunately, if a piper dies, the zombies to not die with it. They must be dealt with next.