Dm Finally Plays Needs Advice

Hey guys, I'm a DM done multiple campaigns for a group of 5 players but I told them I kinda burnt out and asked if one of them can run. So luckily one of my players is gonna run a pre-built campaign and I'm so exited since this is my first time as a player.

So before I go into what I need advice about I should reassure you guys about a few things, I asked my pal (The DM) If I can play a wierd character and he loved the idea of my critical flaw and whatever insane build trying to balance it out.

(Obviously will run it past him, if its truly busted but give it your best shot guys)

So this is the idea, Im playing a Drow Warlock thats all about trying to make a Merchant Industry (Secretly a Cult). Thats the short version of my Goal but the interesting part is that I wanna build him to be an insane character but he's basically blinded (Due to sunlight sensitivity - That gives disadvantages for perception and attacks if in direct sunlight which the DM says will be most of the time and I love it)

Little note, I will not be trying to get rid of it by going under shade and try and play along with it. Like Role-playing a crazy powerful drow thats worst enemy is the sun.

Now here is where Im asking you guys for advice I need help building this character, for example:

- Classes, Should I multi-class or just warlock?

- Feats, Are there any Insane Feats for warlocks, like i hear sentinel is insane for some classes.

Extra Info:

- He doesnt know when this will end so he said we might end around lvl 12 to 16 (Ik wide range)

- I dont mind if its insane character for skills or for combat well as good as he can be in combat due to the sunlight sensitivity.

So generally, I just wanna hear some of your crazy warlock builds and see if any of them catch my eye. Thank you so much guys!