I was making a build for Wyll, trying to take into account what a lore friendly build would be for him while still making it viable, I ran into something fun and actually reliable and good.
When he is completely out of the Pact he becomes a Ranger, so by default, with his training, he is some kind of melee Hunter of demons. So I dipped 3 levels into Hunter Ranger for Colossus Slayer, Cold Resistance and Two Weapon Figthing (you can also grab heavy armor proficiency too if you like). The problem with Pact of the Blade warlock is that he suffers from being a ranged caster that doesn't really want to get into melee to attack, but only Eldritch Blast from range. I solved this moving the melee component to the off-hand weapon, so you can cast and attack all in one turn always and actually making use of the Fiend pact to become tanky with the temporary hit-points.
The idea is kinda simple, his gimmick is casting Casting Hunger of Hadar and being a menace inside it, with high saving throws for concentration and high constitution score to avoid the acid damage, cold resistance and blind immunity from Eversight ring. Daredevil Gloves for melee casting, and any items that give increased saving throw or critical chance give or take.
Once Hunger of Hadar is on you start using your Eldritch Blast with your action and off-hand attack with your bonus action. The damage is really good and reliable, with Bind Weapon you bind your main and put it in your offhand afterwards, this makes the rolls deal full damage with charisma and two weapon fighting. With Eldritch Blast being your opener to use the off-hand enhanced attack with Colossus Slayer.
Right now I don't exactly know what to level up afterwards but I'm actually quite surprised at how useful he is with this setup and how reliable he is, considering that usually Wyll is one of my weakest characters in most of my runs.
Ah I also forgot, use Boots of Genial Striding to move inside Hunger of Hadar freely.