Infinite Caster (5e Subclass)
From D&D Wiki
At level 18 the wizard gets the ability to infinitely cast one 1st tier spell and 1 2nd tier spell they know, and they can ONLY use those spells, not any 1st or second-tier spell. It's not a noteworthy ability, after all it only comes into use when you've run out of spell slots and even then it won't be of much use. But you just HATED the idea of limiting the spells you could cast a day, didn't you? You gave up spellslots entirely... but at what cost? Casting infinite spells comes with a price. A price you're going to have to pay if you want to get rid of that pesky limitation.
- The Sacrifice
At first level, you gain no spell slots. As a matter of fact, you NEVER gain any spell slots. You do, however, gain cantrips at the normal rate.
- Unlimited Magic
At first level, you gain a single level 1 spell. It MUST be from the Wizard spell list. After choosing this spell, you are forced to keep it and it is the only spell you can use. On the plus side, you can use it unlimited times. On the downside, your body isn't used to this power yet and needs time to adapt. After using your spell 5 times, roll a dexterity saving throw. On a failed save, you take 1d6 necrotic damage that cannot kill you and just leaves you at a point directly above unconsciousness if it does enouph damage to get you that far down in HP. The next time you cast a spell, you don't suffer the effects and you must use the spell 5 more times before it comes into effect again. If you succeed in the saving throw, you must use the spell 5 more times before it comes into effect again. This doesn't apply to cantrips.
- Hardened Will
At 3rd level, you have gotten more used to your powers. You now can use the spell 8 times before the necrotic damage comes into effect. You also gain advantage on all dexterity saving throws because your body has gotten more used to having to take strain from the power.
- Basic Mastery
You've fully mastered 1st level spells. You can cast ALL first level spells provided you have the materials, time, and it's from the Wizard spell list. No longer do you suffer any ill effects after using the spells 8 times if they first tier. You also have the ability to use 2nd tier spells, but you only get to pick one. You still suffer the ill effects of SACRIFICE while using 2nd tier spells.
At 10th level, you gain mastery over 2nd tier spells with no ill effects along with unlocking one 3rd tier spell with ill effects.
At 15th level, you gain mastery over 3rd tier spells with no ill effects along with unlocking one 4th tier spell with ill effects.
At 20th level, you gain mastery over 4th tier spells with no ill effects along with unlocking one 5th tier spell with ill effects.
- ALL UNLOCKED
At 20th level you gain access to ALL cantrips. This includes non wizard/sorcerer cantrips.
- Every Spell!
You can use every single spell that exists... but to use it theirs a cost. Firstly it cannot be above the 4th tier. Next if casting at the 1st tier, you must suffer the effects of SACRIFICE WITHOUT hardened will. It also gains the ability to kill you. For everything above that, you will take 3d6 necrotic damage. At 3rd tier and above, you don't take a saving throw and always take the damage. For just 4th tier, it uses up 2 slots whenever you cast the spell (meaning you can only cast it twice before the bad effects kick in).