Well, after 6 weeks, my PC's finally got to the final section of the Sunless Citadel. There were 6 of them, all 2nd level, vs Belak, Sharwyn, Sir Braford, Durnn the hobgoblin chief, and Grenl the goblin cleric. The PC's had: 1 human paladin, 1 ghostwise halfling ranger, 1 half elven roge, one human monk (brother to the paladin), one half elven fighter, and a dwarven cleric.
I changed the spell selections for Sharwyn and Belak, because the PC's had already encountered them once and retreated, so they were better prepared for combat (Sharwyn with a sleep and Color spray instead of the poorly chosen magic missile the module used; Belak's spell selection was set for summon swarm, summon natures ally, and two spells from Magic of Faerun:Blinding Spittle (touch attack at -4 to blind an opponent) and Handfire (basically 1d4 +1/lvl damage, for 4 successful attacks, as Chill Touch)).
The PC's went down hard, mostly due to some very poor rolling and some high ACs (Durnn was boosted by a Barkskin spell from Belak) on their opponents, but at the end of the fight the only ones standing were Belak and his supplicants.
I guess all of that is really irrelevant to my question, however: do Gulthias Tree supplicants gain XP? Since Belak and his allies won, they earned 3600 XP (6pc's @ cr 2 each==6x600xp). If the supplicants do get XP, then Belak only gets 720 XP; if they don't, he gets 1200 xp. Not enough for him to go up a level, but it gives him some more XP to burn on some potions, which will be useful for him and the supplicants. Has anyone else had to deal with this in their campaigns? The surviving characters have made it clear to me that they plan on going back to try and rescue their comrades (unaware that two of them will become supplicants themselves, while the third will become mulch), so I kind of need ot figure out what options are available to Belak when they come back....
I changed the spell selections for Sharwyn and Belak, because the PC's had already encountered them once and retreated, so they were better prepared for combat (Sharwyn with a sleep and Color spray instead of the poorly chosen magic missile the module used; Belak's spell selection was set for summon swarm, summon natures ally, and two spells from Magic of Faerun:Blinding Spittle (touch attack at -4 to blind an opponent) and Handfire (basically 1d4 +1/lvl damage, for 4 successful attacks, as Chill Touch)).
The PC's went down hard, mostly due to some very poor rolling and some high ACs (Durnn was boosted by a Barkskin spell from Belak) on their opponents, but at the end of the fight the only ones standing were Belak and his supplicants.
I guess all of that is really irrelevant to my question, however: do Gulthias Tree supplicants gain XP? Since Belak and his allies won, they earned 3600 XP (6pc's @ cr 2 each==6x600xp). If the supplicants do get XP, then Belak only gets 720 XP; if they don't, he gets 1200 xp. Not enough for him to go up a level, but it gives him some more XP to burn on some potions, which will be useful for him and the supplicants. Has anyone else had to deal with this in their campaigns? The surviving characters have made it clear to me that they plan on going back to try and rescue their comrades (unaware that two of them will become supplicants themselves, while the third will become mulch), so I kind of need ot figure out what options are available to Belak when they come back....
Now Granted your group had 6 PCs not 4. But the group was skewed heavily towards combat with only one magic user (cleric) and no wizard/sorcereror.
It depends on what your players would most enjoy, but I'd suggest giving them a chance to rescue their commrades. Afterall, it probably takes a while for the gulthias tree to completely tranform someone into a supplicant.
If you think of supplicancy as being an infected state, like lycanthropy, then we figured that it could be cured by similar means. We thought it pleasingly symmetrical that a supplicant might only be cured by the fruit of the tree which had corrupted him. 
