This quest is no longer available within the game.
Possessing a Cenarion Beacon allows one to sea a corrupted soul shard on those tainted beasts that are put down for the greater good. I grind shards into a usable reagent that goes into making Cenarion plant salve. We will use that salve to turn corrupted plants into healthy ones again.
In exchange for these shards, I will give you some Cenarion plant salves I have already prepared.