And remember, just to summon a spirit, you roll your magic + summoning skill (about 10-12 dice), versus their force. You have to resist drain (which you should have another 10-ish dice to, at least) versus the amount of successes they get on force.
This means that you can fairly easily and safely call up a Force 5-6 spirit (they're likely to only get 2-ish hits on their roll, you're likely to get 4-ish on yours) to conceal you for as long as you want, or up until the next time the sun crosses the horizon, whichever comes first. That's a -5 to -6 dice penalty for all sensory methods to detect you, period. That's enough to knock out the majority of standard sensors and anyone's senses who isn't super-focused in perception. Throw in a chameleon suit or some sort of stealth roll, and you're very very difficult to see.
Additionally, unlike any spell, Concealment also hides you by an equal amount on the astral plane as well, for no extra charge!
The only spirit types that do not get concealment as a power or optional power are fire and guidance spirits. However, guidance spirits do get the shadow cloak ability, which is a slightly less powerful concealment power. It works the same, except instead of making you invisible, it makes you shadowy. In fact, I'd personally say that fire and guidance spirits overall are on the bottom of the list of useful spirit types.
