Running a game where an allied spirit with the concealment power is having a big impact. My player who the allied spirit belongs to is not doing anything annoying but in reading the power as written it sounds like a spirit can have concealment on itself and cast spells that either attack npc's directly or that the spirit can cast an illusion spell to mess with combat while still maintaining the concealment power. This seems kinda over powered in my opinion but wanted to see what others had ruled in their games as no errata has ever cleared up the point that I know of.

SR4A, p293. Spirits can maintain a number of powers equal to their Magic. Also, "Sustained powers may be maintained over time at no effort or cost."

So no errata needed, it's totally possible and following the rules for a spirit to be able to maintain Concealment and do anything else. Critters with powers are pretty powerful, yeah.

Is Concealment is a physical power? So, if someone uses assensing while astral, the guy using concealment will appear to a reckoning mage?

Concealment is a Physical Power, but SR4A explicitly allows it to be used on the astral plane. Whether it only works on one plane at a time as spells is stated nowhere.

I never thought it was wrong, just over powered. However I did discover I was missing a minor point which is that foes can blind fire to hit the spirit even if they can't see it. That will make things a little better.

exactly what I was going to say. Exactly.

@Stormdrake
With the spirits immunity to natural weapons, blind fire is unlikely to do very much, unless it is a VERY big gun (like, mounted).

I didn't think this would really be such a problem, though. Concealment only removes dice from the perception pool. Unless they are doing something opposed (disguised sniper position, infiltration, etc) then it only takes 1 hit to see them. Especially if it's a team check with multiple people involved.

Also:

Concealment has limitations that have to be considered. If your player doesn't know the above, you can blindside him to take him down a peg.

Krishach, FSPCs tend to be low Force (depending on your reading of it), so stray gunfire can actually be lethal for them.

The few that I have seen tend to have a High Force and Edge, but low Stats. So, your mileage may vary.

I think this is an Ally spirit, though.

Keep in mind that Concealment only helps if a Perception test would be needed in the first place. If they would be automatically noticed without Concealment, they're still automatically noticed with Concealment.

technically true, though I must admit our group has always denied this if the target would have 0 perception dice after the subtraction.

However, you can always force the perception test to be needed. Disguise for sniper blinds, infiltration rolls, and modifiers to these like silenced weapons, would require a perception check to find.