The Doctor

But who tho?

Inventions

Additional spells 

Sonic screwdriver

3rd-level The Doctor feature

At 3rd-level you fix your sonic screwdriver. Your sonic screwdriver works as your casting focus. As well can cast light, mending, prestidigitation, identify, detect magic, knock and arcane lock at will. 

Psychic Paper

Usually, it showed what the holder of the paper wanted the person reading the paper to see or vice-versa.  The psychic paper could change what the user wanted to display in rapid succession.  However, if the user wasn't specific about what they wanted the reader to see, instead using a broad idea like "worst nightmare", what turned up on the psychic paper would always be a surprise.  It could be used to show the reader the credentials of someone they had already been expecting, without any prior knowledge by the user of whom that might be. ] If the user wanted to present credentials as a "higher authority" without specifics, what appeared was a surprise. This even included situations where the user was speaking unrelated babble. Messages on psychic paper appeared in the reader's handwriting. To see if it is fake a creature must pass an insight check verses your spell save DC. 

Sonic Amplification

5th-level The Doctor feature

A number of times equal to your Intelligence modifier as a bonus action or a reaction you can increase the power of any magic item within 60 ft.  You can double the range or increase a + mod by 1 till the end of your next turn.  Remove or add charges. Add your proficiency bonus to DC saves, or to hit. 

TARDIS

9th-level The Doctor feature  

Your TARDIS can look like anything, including invisible, as long as it's in a 5 by 5 by 10 box. To detect it while invisible, a creature must roll an investigation check versus your spell save DC.  The inside is considered to be the same as the magnificent mansion spell. As well, it can cast the Teleport spell on itself and all inhabitants of the TARDIS. The TARDIS can be called to you by activating your Sonic screwdriver and staying within 1 square mile for 24 hours while it finds your location. It also weighs 5,000 tonnes and has a hit point total of your artificer level times 5 and an AC of 10 + proficiency bonus. Any rolls made to teleport are made at disadvantage. If a mishap happens with the TARDIS or its hit points drop to 0, it is not destroyed. However, it is disabled for 1d4 days. 

A working TARDIS

15th-level The Doctor feature

Teleporting with your TARDIS is no longer made at Disadvantage. As well, time can move twice as fast or slow on the inside of the TARDIS. (Talk to your DM about the possibility of time travel and/or travel in space.)