| The Dawnstrider |
You can create a mask using Undead Anatomy I (level 3 arcane spell). It would end up being quite expensive though, the base price would be 30,000gp (level 3 spell x level 5 caster x 2000gp), making it a 60,000gp treasure. If you don't want it to be useful to the party afterwards, it could be cursed to cause the wearer to be subsumed by the psychology of a juju-zombie (say a Will save every round the mask is worn).
Thank you... this is the custom item I was thinking of, but as an amulet. Cursed is a great idea to make it less than useful to the party after they get it.
Ah, the problem is that Non-detection is the best spell for thia, but the text doesn't explicitly state that it stops supernatural abilities, just spells and magic items. You could infer that Lifesense is a form of Divination like Arcane Sight, True Seeing, See Invisibility, or Detect Thoughts. It definitely should be considered a form of divination, even if the text doesn't specifically say so.
If you wanted to be really tricky, you could have him possessed by one of the Ghost Necromancers in the dungeon, which would make him read as both.
This is another excellent idea, since they are already keeping spells up on the NPC that block divination. I could just say in this case that it blocks the lifesense, too, though that feels slightly cheesy.
It seems like this is the big chance for this ability to come into its own and be all that the player could hope for it to be. Of course, you mentioned that the player is difficult, so maybe nerfing a key ability the one time that it would actually be extremely useful is fair play.
Let it work. Don't penalize PCs for getting the right *whatever* to make an encounter easier. Doesn't mean that getting to him will be easy. Just look at the ability and situation, play the encounter out in your head and see where things could go wrong or get confused in a fair and "realistic" way.
So far, the lifesense ability has already totally won the day in multiple encounters. My players, despite their best intentions at trying to separate player knowledge and character knowledge, metagame like mad. And to date, we've let lifesense absolutely pinpoint living things even in a sea of chaos, without concentration (probably my fault for letting it be awesome, but the player feels like their character sucks otherwise, so I've been trying to let this be great). So if lifesense works in this encounter to tell them where my NPC is, even if I try to make it confusing and difficult, they'll just walk through it without the fun of the chaos. So I think making it not work by either blocking the lifesense through anti-divination means, or through a magic item, will make it as interesting as it could be, and make them rely on other skill checks to find the NPC. Especially since they are going to get a huge bonus out of this if successful: the NPC they rescue has quite a few class levels and will join them (and fill in much needed skills the party is lacking due to character deaths) for the rest of the AP.