An item that gives them the ability to create illusions. However after it is used enough times, he starts seeing the illusions he has created and can't distinguish them from reality (or reality from the illusions).
An item that gives him the ability to lie more effectively, but also unable to tell if other people are lying to him. Maybe even eventually he starts to hallucinate that people are saying things that they aren't actually saying. Either way, eventually he becomes paranoid and can't trust anyone.
Lets him hide better / become invisible. Enough uses and he believes that the invisibility has become permanent / he is so good at hiding he can hide in plain sight, but everyone can actually totally see him.
Maybe give them a magic mace in the shape of a jester's scepter. There's a curse attached to it however that forces them to cast one of their cantrips as either a bonus action if they hadn't taken one yet or as an action on their next turn.
They should have at least 4 by level 5 so just have them roll a 1d4.
If that's too much then just combine their preferred weapon with a wand of smile/scowl that activates on a successful hit.
Even roll= smile
Odd roll= scowl
Smile gives a +1 to their next roll
Scowl gives a -1 to their next roll
Perhaps once the player reaches certain thresholds of madness points, it could confer additional effects to him. They could be double-edged swords in a way, both beneficial and detrimental (to fit with the madness idea): perhaps one threshold afflicts the PC with some sort of recurring visions that deal psychic damage to the PC when they happen, but give hints towards a plot point or something that would help the PC out in the long run.
An item that gives them the ability to create illusions. However after it is used enough times, he starts seeing the illusions he has created and can't distinguish them from reality (or reality from the illusions). An item that gives him the ability to lie more effectively, but also unable to tell if other people are lying to him. Maybe even eventually he starts to hallucinate that people are saying things that they aren't actually saying. Either way, eventually he becomes paranoid and can't trust anyone. Lets him hide better / become invisible. Enough uses and he believes that the invisibility has become permanent / he is so good at hiding he can hide in plain sight, but everyone can actually totally see him.
Maybe give them a magic mace in the shape of a jester's scepter. There's a curse attached to it however that forces them to cast one of their cantrips as either a bonus action if they hadn't taken one yet or as an action on their next turn. They should have at least 4 by level 5 so just have them roll a 1d4. If that's too much then just combine their preferred weapon with a wand of smile/scowl that activates on a successful hit. Even roll= smile Odd roll= scowl Smile gives a +1 to their next roll Scowl gives a -1 to their next roll
Perhaps once the player reaches certain thresholds of madness points, it could confer additional effects to him. They could be double-edged swords in a way, both beneficial and detrimental (to fit with the madness idea): perhaps one threshold afflicts the PC with some sort of recurring visions that deal psychic damage to the PC when they happen, but give hints towards a plot point or something that would help the PC out in the long run.