Forgot to answer that. It’s kind of complicated to answer, things made by demons aren’t like what is forged on a physical plane, demons craft a lot of artefacts or weapons but these are usually tied to them, they are made in part out of the demon’s essence and no one else can use them or even take them from the demon except through an excision ritual or if the demon gives or sells it to you, these are called demonforged.
With more efforts, demons can create objects with the very essence of hell, these are usually stronger, much stronger than most demonforged objects but can be taken from them and even be used by mortals, they also cost so much most demons could never afford it, these are called hellforged.
Both, like demons, are able to manifest physically in a physical plane, though they are not as powerful when they have to manifest a physical form. When these weapons get on a physical plane though, they are usually already very old and not easily influenced or altered because they had the time to develop already.
It depends on the size of the bandit group.
Large bandit groups (20+ bandits) will often have a few casters of any kind. Usually sorcerers, pagan divine casters or outcast magic casters in general.
It’s pretty rare for a caster to join a bandit group, because they usually don’t need to. Even a weak caster can easily find a job at The Guild, in a clandestine magic shop, in a mage tower, they have tons of job opportunity, legal or not. But those casters that were exiled, outlawed, or whatever often end up in banditry if they can’t make it on their own.
Casters are usually leaders if they join bandits, because they simply are twice as dangerous as the usual bandit even if they are not particularly skilled.
Smaller bandit bands don’t usually have any casters.