Forgetful Arch Mage

As a young mage with great ambition and promise you sought power in any way possible. Once you reached the pinnacle of your abilities, you got into a battle with another arch mage who destroyed your mind, you wanted to further your abilities by using yourself in an experiment to gain more power losing your memories in the process, or you simply fell to the woes of old age and have gone senile (your choice). Whatever the reason, your mind has been devastated and you now have the long road of relearning and remembering your spells but as you get more powerful the effects on your mind may grow in turn.

Spell memories

At 2nd level you think you start to recall what your spell mastery was, at the dawn of every day roll a D8. Based on the table below that is your mastery for the day of which you gain the "savant" feature for the day.

1 Abjuration

2 Conjuration

3 Divination

4 Enchantment

5 Evocation

6 Illusion

7 Necromancy

8 Transmutation

Forgetful spells

Starting at 2nd level you start either remembering or forgetting how your spells work. Whenever you cast a spell roll a D12 first, if you roll the highest number you cast the spell at 1 level higher than you intended while only expending the slot of the intended level but on a 1 you either cast it at 1 level lower than intended while expending the slot intended or if you are casting at the lowest level you cast a spell of 1 level lower instead of the intended spell but expend a slot of the intended spell with no benefit. If the spell you are trying to cast is of the same school you are a savant in for the day you get the raised spell level of the spell on a roll of 11 or 12. (Cantrips do not need a roll to cast since they are ingrained into you without you needing to remember how to cast them. Also if you are casting a 9th level spell and roll a max on the die you get to cast a level 1 spell as you other action (bonus or main) instead of just a cantrip)

Memories of destruction

At 6th level you start seeing glimpses of your former power. When you cast a spell that damages an enemy you can add 1 additional damage die to the roll. (If the spell uses multiple types of die you add the largest) at the start of your turn roll a D6, on a 6 your memory is clear for a second and you can use this ability again (ability recharges on a 6)

Former master of magics

At level 10 your faint moments of recollection have more clarity to them. When you make any intelligence skill checks roll a D6 first, on a 3 or higher you gain proficiency if you dont already have it and advantage on the roll. 

Forgotten spells

When you reach 14th level your memories swing more than the did, making you forget things that may have happened recently as well as remember some of your older powers. At the start of combat roll a D8, what ever number it lands on you you gain a temporary 1 time use spell slot of that level. Also as a bonus action once per day you can forget that you cast a spell and regain a slot of 5th or lower.