Help needed stating an ancestral spirit NPC

[Luke Bunyip]

One of the PCs in my current campaign (Dungeon Fantasy meets Dwarf Fortress) is a dwarven cleric who's belief system is focused around ancestor worship.
Been thinking for a while of how to accommodate this, and the solution that I've come up with is something akin the Johnny Silverhand NPC in Cyberpunk 2077, or the occasional spectral Jedi from SWs. What I'm after is the spirit of a rather grumpy great grandfather that can provide some magery support for the cleric, as well as some bit of area knowledge, and arcane language translation.

I've had an attempt and stating out a spirit form of a deceased relative of the PC, but I'm not happy with it. This probably a case of switching to the new model of the GURPS Character Generation software.

Thusly, I turn to you, humble hivemind that you are, for your assistance. Specifically what Disadvantages should I include, and some which I should consider.