Think of spell chains as thematically linked spells of increasing power levels. You might assign them spell levels such as 1st, 3rd, and 5th, or whatever suits your game. The spells in this series are largely system-neutral, but should be easily adaptable to any ruleset.
This first one is based on word-play, which is objectively the best spell naming convention. I'm sure I read the word "dementalism" somewhere (perhaps an album title?) but I can't remember where, but it immediately called out for thusly named spells. This one's from my homebrew game in development, Hypertellurians.
Remember kids, use dementalism responsibly.
This school of magic focuses on being out of one's mind for a time, allowing the caster to clandestinely spy on far away locations or people.
I. Prime precept
If you have mastered this level of the spell chain, you can cast your mind into a head-like inanimate object you touch. It must be an item that looks like, and is approximately the size of, a human head. Statues and paintings work particularly well.
When you cast the spell, your body falls into a comatose state and your mind inhabits the object. You see, hear, smell, and feel as if the object were your actual head, though you cannot move it in any way---so your vision is restricted to the direction the object is pointing.
You can keep this up for as long as you can concentrate, or until your actual body suffers harm. Aside from the initial touch, there is thereafter no limit to the distance your body can be from your mind.
II. Improved insight
This spell functions like the prime precept, but it allows you to cast your mind into a living person you touch. Wether or not they notice you doing this depends on how sneaky you are at both the execution, and afterwards at hiding your mind from theirs.
The more active your thinking, the greater the chance of them becoming aware of not being alone in their head. At first, they might develop the feeling of being watched, but if you're not careful your thoughts can mingle with theirs, and among other things, give you away.
III. Advanced aesthetics
Like the improved insight version before it, this mightier version of the spell improves on it in two ways.
- Your body is no longer comatose while it is in effect. You certainly still need to concentrate, and you will appear distracted, but you have enough mastery to both control your physical form, and hide your mind inside your target.
- You may use the inhabited person or object as the origin of any spell you cast.
Needless to say, only the most powerful of spellcasters have ever mastered this mighty version.