This is interesting...
Punching through the watchers keep I'm on level 5, I go up to the 'globe' section and fight my way through that... during the course of the many battles a summoned planetar had maze cast on it by a beholder/brood mother whatever it was, a variance of the beholder anyway.
No worries, I say, continue through the next few battles, rest blah blah the usual. Now I fire down to middle room to do the whole 3 key thing, and before I turn it I go through the whole summon a bit of cannon fodder and my usual planatar. Kind of a nice ally.
Anywho, it tells me "you cannot summon another creature of that type". Well that's a bit weird, nevermind, I'll just rest for a bit and try again. Nothing, same message.
Alrighty, off to the Abyssal Fortress I go. Viola, no wuckin' forries, one summoned planetar.
Rest, let the spell recharge and back to watchers keep 5, go for the summon and bang, "you cannot summon another creature of that type".
Those of you who have been through watchers keep would know a planetar is kinda handy 'bout now.
Neither the planetar or fallen planetar can be summoned?
Was it something to do with the maze spell? Because that's all I can think of!