ToME: the Tales of Maj'Eyal

and hence one of the orbs was inactive. I'm playing nightmare roguelike. not sure if that makes a difference.

I've seen this happen on insane rougelike. Same solution as the guardian just not being there--leave the dungeon, delete the map file for the dungeon, then re-enter. You'll have to fight everything again, but hopefully you'll have the guardians sorted properly. Alternatively, I once somehow managed to glitch myself inside the room you're supposed to use the orbs to unlock the door for by digging next to the un-diggable wall, then using wanderer's rest boots active (telekinetic leap) and I ended up inside the room.

R_D wrote:I've seen this happen on insane rougelike. Same solution as the guardian just not being there--leave the dungeon, delete the map file for the dungeon, then re-enter. You'll have to fight everything again, but hopefully you'll have the guardians sorted properly. Alternatively, I once somehow managed to glitch myself inside the room you're supposed to use the orbs to unlock the door for by digging next to the un-diggable wall, then using wanderer's rest boots active (telekinetic leap) and I ended up inside the room.

That either means that one of the squares in the room are missing a "No teleport" flag OR that you somehow managed to teleport inside a "teleport forbidden" zone. Either way it is a bug.