Demon names are very carefully guarded and typically passed on from master to apprentice (or son/daughter).

They can also be sold, and if bound, name and links passed to new owner and old owner promises not summon the sold demon.

But, should someone summon a bound demon, not their, they really can't bind it, they can torture it and give it orders but those orders are only good in the wizard's presence/range of spells, if the demon gets out of range (of the torture spells) they can escape. A smart demon would escape, but not return to the Abyss (so they can't be summoned again by the guy) and then wait around until the person who summoned it, but was not its bound master was unguarded and kill him/torture him etc.

In general it's a very bad idea to summon a demon who's name you know but can't bind, so very few wizards will do it, except under the instructions of the wizard master.

I don't remember if Hortwell had the ring or not, I don't think he did, but he knew the name and probably had some other device from Lenamare to persuade Tom to do Lenamare's bidding. Lenamare is very good with things like that.

But from what he tells me, Zarg really does like Hortwell. And feels he's better off bound to him than someone else. It might be a bit Stockholm like, but it's also based on experience and looking for the best deal at the time.

It is not unheard of, look at Antefalken and Damien.

Also, I will point out that Shamans and Animages that summon demons often don't use force (they can, or might--but it's a lot more work for them and more dangerous). They often bargain with the demon. Of course, this is a rather dangerous trial and error, but it can lead to very profitable relationships for both sides.

Some of these guys even offer up their souls to the demon in exchange for favors. That's called "hitting the jackpot" Can also happen to djinn's, although not as common as you might think from the tales. In particular, if you somehow bind a djinni against it's will, you have to keep it from returning to Djinnistan or it will tell the others and then you are in the sort of trouble Exador is in.

Demons, unfortunately, don't typically operate that way. Enemy of my friend?, that's my friend's problem, not mine.

UNLESS--you are bound/in service to a higher level demon. So for example, if you were to bind someone in Lilith's service, if your demands interfere too much with her demands on that demon, she'll deal with you (or have someone deal with you more likely) so that you don't annoy her anymore. On the other hand, if she's somewhat ticked/annoyed/bored with her demon servant, the wizard might get lucky and never know how close they were to destruction.

Demons age and grow through their experiences, good and bad, just like everyone else. The demons who don't get bigger, or do so very slowly, generally aren't doing much. E.g. sitting around drinking. However, being bound in service to a master and working hard to figure out how to screw the master over is a generally a good way to learn and grow as a person, and thus get strong. What doesn't kill you makes you strong...unless it just wears you out...