Always dropped by (yellow) Ochre blamish snails (level 15 ones with pointed shells) in the Mort Myre swamps and in the Haunted Woods.
Uses:
It can be crafted into a snelm (snail helmet) at level 15 crafting.
Notes:
You need to have completed the Priest in Peril Quest to access the Haunted Woods and the Mort Myre Swamp (needs also to have at least started the Nature Spirit quest).