L^: d1	-	R#: T	-	D^: 1t + 1r*
C^: s.m	-	CT: 4	-	S^: None
A^: Creature touched	-	psionic encounter: 25%	-	-

Effect: When an invisibility to animals spell is cast by a druid,
the recipient of the magic becomes totally undetectable with respect to normal animals with intelligence under 6.

Normal animals includes giant-sized varieties, but it excludes any with magical abilities or powers.
The magicked individual is able to walk amongst animals or pass through them as if he or she did not exist.
For example, this individual could stand before the hungriest of lions or a tyrannosaurus rex and not be molested or even noticed.
However, a nightmare, hell hound, or winter wolf would certainly be aware of the individual.

MC: Holly rubbed over the individual.
 

Howdy Anson,

The short answer is:

Run the adventure as you think best.

About all I can reasonably comment on is do not make all useful spells non-functional. Invisibility to Animals is one I would allow, for sound will give away PCs if they attempt to use it for anything other than saving themselves from death.

All the rest is strictly your call.