Uninvisible
Getting through the door that blocked the Ninja's head's access, we encounter some more Drow and their minions. It looks like we have stumbled in to the quarters for the guards, and we fight our way through a few waves of fairly weak foes. It doesn't take long to take them all down, so we check out the rooms to make sure we haven't missed any that could ambush us. The Mage, somehow being an expert in architecture and building design despite having taken no Knowledge ranks in that, wonders why the corridor should extend a further 20' unless there were a secret door at the end, and looks all smug when the Ninja manages to find one there. The smugness doesn't last, when, having stayed at the back of the party, he is nearly ambushed by more enemies.
Luckily for him, Grot and I manage to get ourselves between him and the attackers before they manoeuvre further in to position. We see that we are facing two Orcs, two Grimlocks, and two Drow. The Ninja uses his ghost-step ability to become invisible for a round and gets his extra attack damage against one of the Orcs, killing it quickly. This, however, opens up the space for one of the Grimlocks to charge.
With the Ninja invisible and my Monk standing behind him, the DM questions what happens when someone tries to charge through a square occupied by an invisible creature. A short discussion breaks out on the possibilities of the Ninja electing to let the charging character pass, although the Grimlock would finish the charge in his square if it attacked me so what happens then, and so on. The discussion ends when the DM remembers that the Grimlocks have Blindsight and so can 'see' the invisible Ninja. D'oh. The Grimlock simply charges him instead of me. Huzzah!