Master of One Magic

My original post for this subclass was just the bare bones mechanics for what I wanted to try in the future, but I thought I would flesh it out a bit more. The concept for the subclass is a wizard that instead of having a huge spellbook with answers for every possible situation instead learns how to use a few spells they research in a very versatile manner. This is a very common trope in fantasy that after some research I found is referred to as the "Master of One Magic." Examples from both anime and western novels and television include many of the wizards of Harry Potter, the mages of Fairy Tail, the magicians of Mahouka Koukou no Rettousei, the magic from Mistborn, and the magic from the Stormlight Archive. The main reason I wanted to make this subclass though is for two reasons. First mechanically, I wanted a wizard that would be able to adequately fill a damage role because I was having trouble playing a wizard in a campaign that was balanced in terms of classes and roles but had several new players that ended up building their characters in pretty unoptimized ways. Normally that wouldn't be a problem, but we had a DM that tends towards the more difficult and unforgiving and our main damage dealers weren't very optimized. I found out quickly that while wizards make great support casters with amazing versatility; they aren't really able to carry a party through a lack of damage especially at the low to mid levels. There is a wizard build that helps address this issue, the Nuclear Wizard, but it involves an early multiclass into Hexlock and then a later multiclass into Fighter for Action Surge, and I wanted to play a pure Wizard. The only way I could think of to reasonably give the most versatile class a big bump in damage output was to also take a big slash at that versatility which gave me the idea of the "Master of One Magic" caster. Second, lore wise, I think that the idea of a "Master of One Magic" is really neat. This wizard would spend a lot of time learning how to use a spell perfectly and in different ways, which is why I introduced metamagic into the subclass. It makes more sense to me that a wizard who spends years learning how to cast their spells would be able to change how they work than a sorcerer who inherited their magic from a magical creature. I like the way I implemented metamagic for wizards in that a sorcerer uses metamagic by manipulating how magic itself works while a wizard uses it by manipulating the design for the spell they are casting. In exchange for taking much more time and effort to learn a spell as well as much more effort to prepare it; these wizards cast those spells more powerfully and dynamically. I was aiming for a powerful but not broken subclass, but I haven't been able to actually try it in a campaign yet so it could be mediocre or it could be absolutely busted. Let me know if I've made any mistakes or if you have any suggestions for balancing it better. Thanks for reading!

"The 'Master of One Magic' is a wizard that spends a large amount of time and effort to learn and master a few specific spells. Their efforts to accomplish this lead to them knowing less spells and having more complicated spell designs to prepare, but they believe that those costs are mitigated by how much more powerful and versatile their favorite spells are. The 'Master of One Magic' might not be able to come up with the perfect spell for any situation, but, if they specialized in fireball and you need a fireball,  it'll be the most powerful fireball you've ever seen."

Enhanced Power

When casting a spell that you have specialized in you may add your intelligence modifier to any damage roll of that spell.

If the spell has multiple targets, for example scorching ray, you may add your intelligence to each beam, but if the spell has multiple rolls on the same target, for example hex on top of ray of frost, you only add your intelligence modifier once.

Specialization

As a wizard you decided that it was a better use of your time to truly master a few spells instead of knowing many. From now on you only learn one additional spell when you level up and it costs twice as much gold and time to learn a spell from a scroll. Choose a metamagic option to learn from the sorcerer list of metamagics including Careful, Distant, Empowered, Extended, Heightened, Quickened, Subtle, and Twinned. Whenever you take a long rest you may choose a spell to specialize in. Your maximum number of specialized spells is equal to your proficiency bonus added to your intelligence modifier so choose carefully. You may not specialize in cantrips. You may only specialize in spells from the wizard spell list that you learned as a wizard. You may not cast specialized spells except by preparing and using them as a wizard. Preparing a spell under 4th level that you have specialized in counts as preparing two spells, preparing a specialized spell under 7th level counts as three, and preparing a specialized spell above 7th level counts as four. Whenever you cast a spell that you have specialized in you may choose to cast it with a learned metamagic option.

You may choose to learn an additional metamagic option at 5th, 11th, and 17th level.

Intuitive Understanding

Magic that you have specialized in has become easier to cast. A number of times equal to your proficiency bonus per long rest you may cast a prepared specialized spell at its original slot level without a metamagic option without expending a spell slot. This may be done according to the timing restrictions of the spell you cast.

Masterful Implementation

You may add your proficiency bonus minus 2 to the save DC as well as your proficiency bonus again to the to hit modifier of specialized spells that you cast.

Extract Maximum Potential

Whenever you use this feature you gain two levels of exhaustion. You may cast a specialized spell with up to three metamagic options. Creatures automatically fail saves against this spell and it is cast as the highest level of spell slot you have without expending a slot. If it is capable of being a critical hit it automatically is.