Artisan of Magical Foci

The crafting of a magical focus is a common enough thing for a spellcaster, but there are a few who choose to study and specialize in such work. Combining elements of carpentry, gemcutting, metalworking, taxidermy and glassblowing true artisans master the craft to create fantastic new foci for their own use first, but later for others' use. 

Crafting Focus

Beginning when you select this school at 2nd level, you learn how to carve, forge, engrave or otherwise craft and create a physical object to be used as a spellcasting focus. You gain proficiency in one type of tools. Artisans of Magical Foci tend to specialize in a particular form of crafting - staves, wands & rods, orbs & crystals, jewels & reliquaries, etc.

Creating magical items costs half the normal amount and takes half the normal time indicated (DMG p129) -  thus a common magic item costs 50 gp in materials and takes sixteen hours to create, an uncommon item costs 250 gp and takes 80 hours to create, a rare item takes 2500 gp and 800 hours to create, while a very rare item costs 25000 gp in materials and takes 8000 hours to create. Legendary items (aside from your sentient foci described later) still cost the full amount and time listed in the DMG. At the DM's discretion, time can be reduced by having assistance during the crafting process, and costs can be offset by rare or exotic materials found in the course of adventuring. 

During a Short Rest you can attune to a focus you created, granting a +1 bonus to your spell attack rolls and spell save Difficulty Class when wielding the focus. This attunement ends after a number of days equal to your wizard level and the focus will break, crack, crumble or become otherwise unuseable.  You can preempt this by spending another Short Rest reattuning to the focus before it expires, extending the attunement by a number of days equal to your wizard level. 

Sentience

Beginning at 2nd level, when you attune to an arcane focus you created, you can grant it Sentience - that is, a personality all its own. The focus gains Intelligence, Wisdom and Charisma attributes up to your own ability scores, which may be taxing upon your psyche. Roll 1d20 for each ability score. If it exceeds your own attribute, the focus' score is equal to yours, and you suffer a penalty to that attribute equal to the amount it was exceeded by until you complete a Long Rest. An ability score reduced below 3 results in unconsciousness, while an ability score reduced to 0 or below results in death. Thus it is ill-advised for any wizard with Intelligence, Wisdom or Charisma scores lower than 11 to attempt such crafting.

A sentient focus has hit points equal to your wizard level, takes no damage on a successful saving throw and half damage on an unsuccessful one, and an armor class of 15. It has blindsight within a 10' radius, and can communicate anything it perceives telepathically to you while in physical contact. If the focus has an ability score of 13 or higher, you can shift concentration of a spell from a spell-list associated with that ability score to the focus, freeing up your own mind to concentrate on another spell.

Persistent Energy Focus

Starting at 6th level, you have learned to create a focus for your own use which grants a +2 bonus to spell attack rolls and saving throw difficulty class.

If you choose not to use this ability, you can instead create magical spell foci which persist after you no longer possess the item, if it is attuned to someone else. You may create foci (arcane, druidic, holy or unholy) for others to use, granting a +1 bonus to Spell Attack rolls and Saving Throw Difficulty Class when wielded. You and the recipient must spend at least 4 hours engaged in a ritual to attune the magical spell focus to them, which remains attuned to them for a number of days equal to your wizard level. They may re-attune to the item during a Short Rest, renewing the power for the same number of days. These temporary foci intended for others use cannot be sentient.

Foci of Spell Storing

Beginning at 10th level you can store spells within your sentient focus. The sentient focus can store one cantrip with unlimited uses and spells, and total spell slots not exceeding half your wizard level and charges equal to your wizard level. A spell uses a number of charges equal to its spell level when cast. The focus regains 1d10 charges each day at dawn. A sentient focus' spells must be selected at the time of it's creation and cannot be changed by any means short of a Wish spell. You or someone assisting you must cast each spell or read it from a scroll at the time of the sentient focus' creation.

You can adjust the ability scores of your foci upward by spending an additional hour for each point you adjust, and take a penalty on your own ability score equal to the number of points adjusted until you complete a Long Rest. Any sentient focus you create from 10th level onward is a permanent magical item which will persist in the hands of any other wielder who attunes to it. Being tied to your own psyche, this is especially dangerous if one of your sentient foci fall into the hands of an enemy. You are vulnerable to psychic damage and have disadvantage on spell saves cast by a wielder of your sentient foci.

Artifact Creation

Starting at 14th level, you can imbue a focus you create with a +3 bonus to Spell Attack rolls and Spell Save Difficulty Class. 

Having mastered imbuing a focus with a small piece of your own sentience, you have learned to imbue a focus with the sentience of another creature, whether living or recently dead. If the creature is alive and unwilling, or died within the past ten days, it makes three saving throws (Intelligence, Wisdom and Charisma) against your spell save DC. The sentient item's abilities start equal to the creature's. If it succeeds on a saving throw, that ability score of the item is reduced by 1 and it gets to make another set of saving throws in an hour. If it fails all three saving throws, the crafting is complete. If any attribute is reduced below 10, the item is considered cursed and will actively work against its' creator or wielder whenever possible. If an attribute is reduced below 3, the entire crafting fails and the focus is ruined.

Extraplanar creatures (celestials, fiends, elementals, genies, fey, etc) cease to exist outside he artifact. Other unwilling living creatures suffer 1d6 levels of exhaustion, with 6 resulting  in death for the creature. A willing living creature may suffer penalties to it's ability scores as described previously for you, the artisan, but also suffers three levels of exhaustion. 

Sentient Artifacts may cast spells as previously described, but gain charges equal to the creature's challenge rating or total class levels, rather than your wizard level.