Thanks, Trinite, my group arrived at Aarons hideout yesterday and I went with your funny, little RP encounter. When the parties rogue sneaked into his encampment, he heard some shuffeling from inside the lean-to and then some zombie-esque noises that I made up. When they then entered a few minutes later the noises started again and they noticed this corpse hanging from a noose, making scary noises and the potion with his last will, right next to the door.
They read it and one of the PCs threw a javelin at the corpse for good measure and it was quite fun doing my best zombie impression "woah ...groawlaaaaaarggggghh ya bastard hit me in da hip, ya dirty swab!!!!"
And then they befriended him and he told them how to get into the grindylows cave and he agreed to help them out if they took him with them to their ship. Aaron ended up diving into the pool to get Sandara out, so he was quite useful and peeps generally liked him enough.