GMMichael
Guide of Modos
Cantrips means a caster is never without some magic, spell slots are versatile but concentration and the limited number will keep them from being abused.
Never without magic? So, my dream that was born with the 3rd edition (and 3rd sequel FF) warlock continues:
Emperor Gestahl, here is your army of magic-spewing slaves. Their power output is nigh-unlimited, which means that your slave-empire will ultimately crush those freedom-loving kingdoms! Mwa ha ha ha ha!
(insert Kefka laugh here)
Seriously though. If I allowed warlocks in my game, 99% of them would be on a chain gang, using magic missiles instead of pickaxes, and casting fire orbs into the forges of respectable, hard-working, clichèd dwarf smiths.