Starting at 2nd level when you take this subclass, you can add 1 transmutation spell to your spellbook for free. Whenever you gain a level in this class, you may add another transmutation spell to your spellbook for free.
Additionally, the time and gold it takes you to copy transmutation spells into your spellbook is halved.
Starting at 2nd level when you select this school, you can create Transmutation Circles to cast spells. You can cast spells that are 3rd level or lower, have a duration of instantaneous, and a casting time of 1 action with Transmutation Circles.
When you cast a spell with a Transmutation Circle, it requires your action on your turn to begin scribbling the runes of the spell on a surface, such as the ground or a wall. When you create the the Transmutation circle, you must decide the area of effect or the target of the spell and cannot change it. You must then concentrate on the Transmutation Circle until the start of your next turn.
At the start of your next turn, if you have successfully maintained concentration on the Transmutation Circle and have not moved, you can use your action to cast the spell without expending a spell slot. If you lost concentration or moved, the Transmutation Circle fails, and you cannot cast the spell.
Starting at 6th level, when you finish a long rest, you can create a transmuter's stone that stores transmutation magic. When you create the stone, choose a primary and secondary benefit from the options listed below. While you hold the stone, you gain both the primary and secondary benefit from the stone, but if another creature holds the stone, they only gain the primary benefit. You may also use your transmuter's stone as an arcane focus.
You gain darkvision out to a range of 60 feet
You gain an additional 10 speed while unencumbered
You gain proficiency in Constitution saving throws
You gain resistance to acid, cold, fire, lightning, thunder, bludgeoning, piercing, or slashing damage (you choose the type when you make the stone)
You gain a Swimming or Climbing speed equal to your walking speed. (you choose when you make the stone)
You gain the ability to breathe underwater
You can add your intelligence modifier to the damage rolls of your spells
An ability score of your choice increases by +1 (you choose the ability when you make the stone)
Each time you cast a spell of 1st level or higher, you can change one of the effect of your stone if the stone is on your person. If you create a new transmuter's stone, the previous one ceases to function.
Whoever has the transmuter's stone can transmute one object composed entirely of wood, stone (but not gemstone), iron, copper, or silver, or pyrite (fools gold), transforming it into a different one of those materials. For each 10 minutes you spend performing the procedure, you can transform up to 1 cubic foot of material. After 1 hour, or until you lose your concentration (as if you were concentrating on a spell), the material reverts to its original substance.
At 10th level, you can inscribe more complex Transmutation Circles. When you cast a spell with a Transmutation Circle, you can make one modification to the spell on the fly, such as altering damage type, range, or save type, as detailed in the Modifying Spells feature. You do not suffer any of the negative penalties for modifying a spell when cast through a Transmutation Circle. You can cast a spell with a Transmutation Circle that doesn't meet the normal requirements (such as being 3rd level or lower, instantaneous duration, etc) if you expend the proper spell slot for it.
Additionally, you can cast a spell of 6th level or lower with a Transmutation Circle without expending a spell slot even if it doesn't meet the other requirements as long as it is from the transmutation spell school. You can use this feature once before you must take a short or long rest.
Starting at 14th level, you can use your action to unleash a reserve of transmutation magic stored within your Transmuter’s Stone in a huge burst. When you do so, choose one of the following effects. Your Transmuter’s Stone cannot be used this way again until you finish a short or long rest.
Major Transformation. You can transmute one nonmagical object—no larger than a 10-foot cube—into another nonmagical object of similar size and mass and equal or lesser value. You must spend 10 minutes handling the object to transform it.
Panacea. You remove all curses, diseases, and poisons affecting a creature you touch with the transmuter’s stone. The creature also regains all its hit points and loses up to 3 levels of Exhaustion.
Restore Life. You cast the raise dead spell on a creature you touch with the Transmuter’s Stone without expending a spell slot or needing to have the spell in your spellbook. The target doesn't have any penalty to rolls due to the effects of the raise dead spell when cast this way.
Restore Youth. You touch the Transmuter’s Stone to a willing creature, and that creature’s apparent age is reduced by 3d10 years, to a minimum of 18 years (or the equivalent adult age of the species). When you use this effect on a creature other than yourself, it doesn’t extend the creature’s lifespan.
Pure Transmutation. Cast a spell of 5th level or lower without expending a spell slot or material components. It does not need to be from the Wizard spell list, and it does not need to be a spell from your spellbook.
Diminutivity. You touch the Transmuter’s Stone to a willing medium or small creature. The creature’s size becomes either tiny or large (your choice) for eight hours, or until either you or the creature wills the effect to end. While large, the creature deals an extra 1d4 damage on weapon attacks and has an extra 5 feet of reach. While tiny, the creature has a +2 to AC, can move through medium or larger creatures spaces without costing any extra movement, and doesn't provoke opportunity attacks.