NOTE: Homebrew must be allowed for this to work!
- Take 1 level in Rogue to get Sneak Attack. Take 5 levels in Warlock (this is preferably your starting class).
- Take Agonizing Blast at the second Warlock level, as well as whatever other invocation you want.
- At fifth level, take the dandwiki homebrew Eldritch Blow invocation, which goes as follows:
As an action, you may make a melee attack against a creature, dealing additional damage equal to your eldritch blast's damage on top of the existing weapon damage.
- Get a rapier since sneak attack requires a ranged or finesse weapon.
This should get you 1d8 + DEX piercing, at least another 1d6 due to sneak attack, as well as 2d10 + CHA force damage. I say 2d10 because at 5th level, you get another d10 for Eldritch Blast damage.
This should work, right?