OCC: Com'n Callista. Don't keep us guessing any longer. Will Holly betray her friends to become a queen? Or will she, hopelessly overmatched, fight Belzar? We're waiting to see what your character decides...
Also OCC: For everyone, I didn't describe the bog shambler very well. I got the idea from "Dungeon Hack"; an old PC game from the 80's. The shambler is basically 2000 pounds of vegetation such as you might find in the deepest and most ancient swamps. It's primitive, basically immune to fire (so wet), and cold because it's so thick (Water really takes a long time to freeze, if you understand the freezing process), while at the same time it moves pretty fast. Since it has a lot of solid Cypress wood in it, it hits really hard. Then, it grabs its enemies with its many fast-moving, stick-to-anything vines and pulls them inside to crush and digest. Extra protein, for a crunchy snack.
Few know the primitive language of bog-shamblers. Its thought processes would be quite alien to most flesh-and-blood creatures. (Being one of those, I have no idea what they would be.) However, this one serves Belzar when summoned. Belzar gives him/it the aforementioned "crunchy snacks" and sends him/it safely back. It does not feel pain, per se, but does not like being damaged either. It has no eyes, but senses light, heat, sound, and like all plants has extraordinary chemical sense. Sort of like smell/taste.
Belzar has quite a number of willing subjects available for various reasons. Some, like the paladin, serve in an unwilling fashion. Some, like Melgrittizgym, are summoned at great risk. It's always easier to summon someone than to control them; especially if they're intelligent and have their own ambitions.
The bog-shambler Atta-frema-vernus really likes to order out from L.B. Belzar's All-Night Deli and Hero Sandwich Delivery Service, since the shamblers have cleaned out most of the big game from their swamp, and they can't move out of it. With consideration of the above guidance, you can use him to fight your guys if you want. Have fun!
If you need to use Belzar for something, remember some rules (I just made them up, but hey):
1) Summoned beings who are willing (minions) come easily, and after a moment's confusion, are ready to help Belzar.
2) Unwilling summoned take lots of effort to summon. Even more to control.
3) Summoned inanimate objects are things Belzar has seen before (if they're small) or marked in the past (if they're large). He inscribes his mark on almost everything he can get his hands on.
4) It is much easier to summon an inanimate object if the summoner sends back an equivalent amount of similar mass that is near at hand. Distance doesn't matter much. Of course, that can create a big hole... which makes an exceptionally useful thing to summon!
Belzar can also do the usual wizard tricks in a pinch, but he is at heart an Arch-Summoner.