Possibly a +X bonus to AC and saves?BOZ said:Foresight (Su): The tween has the ability to see a few seconds into the future and can telepathically warn its host of impending danger. Neither the recipient nor the host can be surprised or caught flat-footed.
I'm wondering if "a few seconds into the future" shouldn't be changed to something else? I do like the part about not being caught flat-footed.
BOZ said:I think the infestation needs to be written up as an ability. As I suggested before, one model can be the "conversion-that-will-not-be-named", though this would be much less complicated than that creature.
"Once a host has been selected, a tween will remain permanently until the host or the tween dies, Neither tween nor host are able to voluntarily sever the bond. If the host of a tween dies, the shock and grief of losing its host will literally cause the tween to split in two, causing the birth of a new tween. Both tweens then will usually begin looking for new hosts, the "old" tween almost immediately, and the "new" tween as soon as it finds out how miserable its life as a tween on the Ethereal Plane can be.
There are rumors about some magical research that has been done on the nature of tweens - more specifically on how to separate a tween from its host without the death of one or the other. A wish spell has been proven effective, and experiments have been done with combining dispel magic, remove curse, and plane shift, but thus tar the results of these experiments have been disastrous. An amulet of proof against detection and location will usually discourage a tween from infesting a character in the first place. The tween prefers to choose an intelligent host, and it cannot gauge a being's Intelligence in the presence of such an amulet."
BOZ said:Now, the text never says (as far as I noticed) whether the host has to be willing or not. In fact, it seems that more likely than not most creatures (except loners) would not want a tween inhabiting them. Maybe then a incorporeal touch attack and saving throw (both can, of course, be intentionally failed by a willing host) would be necessary for infestation?
BOZ said:Also, the tween must have some sort of mind-reading ability, since it is said to look for intelligent hosts, and if something blocks its ability to assess a potential host's intelligence it will skip that creature.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.