Chris Lindsay here to tell you all about my new favorite subclass... the Thaumaturge!
 
If you ask a player that enjoys playing an arcane spellcaster what they'd like more of, there's a good chance they might answer you with... the ability to participate in more encounters using the magic that is their stock in trade meaningfully... or simply put, they want more spell slots. 

The Thaumaturge is my homage to the classical magic user from days gone by. They don't have a lot of fancy tricks or gimmicks like wizards with other subclasses, but what they do have is the ability to simply do more. At their most powerful, their connection to the foundational forces that shape the mystic arts is second to none. Wherever it is that magic comes from in your setting (ley lines, dragons, mystic rituals and formulae), or in our case, the Phlogiston, the Thaumaturge is a master of drawing more power from these sources than any other wizard.

Phlogiston is the substrate from which both subtle and dramatic mystical phenomena emerge. Those individuals attuned to arcane, divine, or primal energies draw power from Phlogiston to accomplish feats of pure wonder. 

     There is a small subset of arcane spellcasters that profess to follow the school of the Thaumaturge. A school devoted specifically to the study of Phlogiston and its raw application in the manipulation of the arcane at its source. While not as demonstrably impressive as more specialized wizards a Thaumaturge is a power to be reckoned with, nonetheless. 

When you select this school, you gain Expertise in two of the following skills or tools in which you already have proficiency: Arcana, History, Investigation, Medicine, Nature, Religion; Alchemist’s Supplies, Brewer’s Supplies, Glassblower’s Tools, Herbalism Kit, Jeweler’s Tools, Painter’s Supplies, Poisoner’s Kit, Potter’s Tools, Tinker’s Tools, Weaver’s Tools, Woodcarver’s Tools. 

     At 6th level, you can choose two more skills from this list to gain this benefit. 

When you use Arcane Recovery to regain some of your magical energy, the number of spell slots you recover are equal to your Wizard level. For example, if you’re a 4th-level Wizard, you can recover up to four levels worth of spell slots. You can recover either two 2nd-level spell slots, one 2nd-level and two 1st-level spell slots, or four 1st-level spell slots. 

You can select one nonmagical arcane focus and infuse it with power drawn directly from Phlogiston. That arcane focus will add +1 to your spell attack rolls and your spell save DCs. If you lose this item, or it is destroyed, you can select another to infuse with this power. If the former arcane focus still exists, it ceases to be magical. The arcane focus only functions for you, though it does not take up one of your attunement slots. 

     At 11th level the bonus your empowered arcane focus provides increases to +2. 

     At 17th level the bonus your empowered arcane focus provides increases to +3. 

You have become powerful enough in your ability to manipulate Phlogiston, that you can temporarily bypass or overcome the Magic Resistance trait of a single creature. You can do this a number of times equal to half your Proficiency Bonus, rounded up. Once you have done so, you cannot use this feature again until you have completed a Long Rest. 

You have become so in tune with Phlogiston that you can use the Arcane Recovery feature a number of times equal to half your Proficiency Bonus, rounded up. Once you have done so, you cannot use this feature again until you have completed a Long Rest.

     Additionally, you may now use this feature to recover spell slots of up to 9th level, though you are still limited by what spell slots you normally possess.