Level 1 warlock with 8th level spell, how to break?

[stoutstien]

So my new GM had us make randomly generated characters. I ended up with a pact of the fey warlock. But he also gave us a random feature from our class and I ended up with Mystic Arcanum granting me an 8th level spell slot once per day. What's the best way to exploit this? Best I could come up with is casting Armor of Agathys on myself and getting other low level creatures to attack me.

You actually can't do that because of how MA works. Those spells are exclusive to that feature so you can't cast a normal warlock spell into them.

Glibness for just stupid social fun or maddening darkness for a huge aoe that does good damage with a long duration.

Feeblemind is ok but those top 2 are the ones that seem the biggest impact at low levels