When summoned to teach a new spell/style the summoned demon remains as long as is required to impart the knolwedge of the spell to the scholar.
Conan RPG: p 223 said:
The duration of demonic pact will always be sufficient fo the sorcerer to learn the new spell from the demon.
How long learning new spells takes is never specified, being one of those things that is usuall assumed to occur "off screen". Basically however long you as the GM wants.
The spell makes no mention of any restictions, such as summoning circles or the like, being placed on the demon. The only restriction mentioned is that he departs at the end of the spells duration since it is the spells magic that is allowing him to remain. The demon of a
demonic pact spell should be a special character, a NPC that the DM puts some thought into, and probably more powerful than the scholar who is calling him. The spell says that if you summon the demon for some task besides learning a new spell that
the sorcerer can call up the demon by casting demonic pact and make a deal that it will perform a specific task for him ... such a task is always at the demon's discretion
In other words the scholar has to deal with his demon to get it to do something. The demon does not have to agree if he does not want to but if he does not agree to any task the spell ends and he goes home. If he does agree to a task he is bound to follow the letter of the agreement
because it is a demon, it may well attempt to twist the sorcorer's words, so that it performs to the letter but not the spirit of the task.
Once a task is agreed upon the only way to give the demon a new task is to summon him again.
So what happens if something unexpected happens while a demon is present such as a barbarian kicking in the door? The demon is bound to perform his task to the letter, if nobody can convince the demon (or he can't convince himself) that new action still falls within the letter of the agreement then he cannot and will not take any action. For example: if a demon was summoned to teach a spell his task is "teach me the ______ spell". When the barbarian comes kicking in the door the demon may, depending on his temperment, sit back and watch the fun until the scholar argues that he cannot finish learning the spell until the barbarian is gone and so the demon must dispatch the barbarian in order to complete his task. At this point the GM will conisder the demon's temperment and relationship with the scholar and either decide that the demon will help the scholar kill the barbarian or respond "My job is to teach you the spell, not provide a suitable environment for learning. I will be waiting here to finish the lesson if and when you finish dealing with the intruder". As you can see there may be some advantages to giving a demon vague instructions that are open to intrepretation, then again there are disadvantages as well :twisted:
Above all remember that the demon of a
demonic pact spell is an inteligent creature with free will and malicious intent. He does have a long-term bargain with the pact-holder and is compelled to complete the letter of any task he agrees to and then leave at the end of the duration of the spell but otherwise he is an independent agent.
It is a generally accepted fact that any creature may defend itself if attacked regardless of whatever other restrictions may have been placed on it.
One more thing. The scholar who learns
Master Words and Signs does not summon that demon to learn new spells (after the first time he learns the master words from it) or indeed to perform any future task.
Once you have successfully cast this spell once, you no longer have any particular need to cast it again.
Hope that helps.