IDEAS? Single-spell Caster

[Elon Tusk]

The idea of a class that can only cast a single spell was mentioned on this forum months ago as a possible new class.
I thought it was clever and started thinking about how to create that, but I'm getting stuck - as one might expect with such a limited toolbox - and need help.

Utility, flexibility, and variety are sacrificed for intensity, specificity, and focus.

I'm thinking that aspects of spell casting can be varied as the class increases so that such things as time, range, components, duration, area of effect, intensity/damage, and number effected improve.

I think having more control of the singular-focused spell could also mean gaining abilities for that spell like:
- detect it [if it is in a spell book, on a scroll, memorized by a caster],
- have resistance to it then immunity to it then counter spell it,
- alter it when others cast it, etc.

The singular spell, I think, could be from any class spell list.

BUT HERE IS THE BIG ISSUE:
Do I limit the choice of spell to lower level spells? If so, what level(s)?
If not, how can one nerf a Wish or anything of the higher ilk at first level?
What kind of mechanics could make this work?

I'd love some brainstorming!


Thanks in advance.

 

[Axios_Verum]

How to make a single-spell caster.

Be a high-elf rogue (assassin). One spell, booming blade, that you will cast every time you make an attack.

 

[Quickleaf]

[MENTION=6875235]Elon Tusk[/MENTION] If you want something like that, I'd say the True20 powers system would be a better starting point than D&D spells.

 

[ThunderDM]

I'd give the PC a scaling 1d10 force damage cantrip similar to Eldritch Blast, then give them spell points each level from the DMG page 288 and allow him to spend a certain number of spell points when casting the cantrip to enhance it in some way. Spending spell points increases the cantrips damage, or range, or makes it an aoe cone, or requires no verbal or somatic component, etc. One spell that can be enhanced through the use of spell points.

For example, at first level he has the Arcane Missile cantrip (refluffed eldritch blast) and 4 spell points. Spending 1 spell point increases the damage of Arcane Missile by 1d10 force damage and allows it to affect an additional target within range. He can burn all four spell points on one massive aoe damage fest but then he's got nothing else to do until he takes a long rest, or he can use a spell point here and there and try and save them.

 

[Elon Tusk]

I'd give the PC a scaling 1d10 force damage cantrip similar to Eldritch Blast, then give them spell points each level from the DMG page 288 and allow him to spend a certain number of spell points when casting the cantrip to enhance it in some way. Spending spell points increases the cantrips damage, or range, or makes it an aoe cone, or requires no verbal or somatic component, etc. One spell that can be enhanced through the use of spell points.

For example, at first level he has the Arcane Missile cantrip (refluffed eldritch blast) and 4 spell points. Spending 1 spell point increases the damage of Arcane Missile by 1d10 force damage and allows it to affect an additional target within range. He can burn all four spell points on one massive aoe damage fest but then he's got nothing else to do until he takes a long rest, or he can use a spell point here and there and try and save them.

That's very similar to what I had in mind.
Here's my WIP single-spell caster:
http://www.enworld.org/forum/showthread.php?549534-Single-spell-Caster-amp-a-Feat-based-Class

 

[TwoSix]

I'll be honest, I don't see a way to do it without using custom designed subclasses around a particular spell. How would you balance a character based around magic missile, versus bless, versus silent image, just looking at 1st level spells?