Mortaccio build
He is the master of Amount (number of projectiles), so try to grab weapons that benefit from his progressive Amount increases.
Weapons: Bone (starting), Wand*, Knives*, Bible*, Runecaster, (any)
* = evolve the weapon
Passives: Duplicator, Attractor, Empty Tome, Bracer, Spellbinder, (any)
The (any) can be whatever you prefer. Garlic is not a bad choice, to breeze through the first half of the game.
Try to focus on upgrading and evolving one weapon at a time.