Nalen

Nalen is gracious in his way once you have succeeded in convincing him you are not in league with the demon slaad taking over the swamp. He is able to instruct the party on the life cycle of the slaad, and, in particular, what dangers to look out for when encountering the slaad. Of particular danger are the red slaad, which can implant an egg in an open wound, and the blue, which can infect you with a plague that can turn you into a slaad. This information can be important when encountering them in the wild.
Nalen also is in possession of a large number of spells, potions and scrolls that will help cope with the dangers the slaad bring. He is willing to part with some of them, but vascillates depending on his mood. If the party want a scroll or potion and offer a reasonable price or trade, he will trade. If the party acts greedy or asks too many questions, he begins to get antsy, and will demand high prices or refuse to deal outright.
While you are being entertained, two red slaad slip up the path outside. Since you tripped many of the alarms on your way through, and Nalen hasn't been able to reset them, the slaad are able to walk right up to the door. When they burst into the room, Nalen will freak out, believing you have conspired against him and brought the demons with you. Cursing you, he will hastily gather up his stuff and begin lashing out against the slaad. Occasionally, if anyone gets close to him, he will turn on party members as well. Once his hackles are raised, he will become distrustful of everyone, and be very difficult to calm again.
If matters start going badly for the slaad, one of them will rush at Nalen, wounding him and infecting him with an egg. Despite his understanding of the slaad and access to curatives, he will become hysterical and rush off into the swamp, leaving the party behind with the slaad. Once the slaad are defeated, you can gather some of the scrolls and potions - either taking them, or leaving some form of payment.
Unfortunately, Nalen doesn't return while you are there. He has been infected with a slaad egg, and thinks his life work has been for naught, and evil has consumed him. He will hide in the swamp.