Elemental Crits

This build stacks as many dice on your attacks as possible and expands your threat range to double all of them. Dark Urge origins can potentially get down to rolling crits on 11 (for a crit rate of 75% with advantage), but realistically you will be able to consistently get down to 14 (58%). The build is also a bit unusual in that you won’t really have a primary ability score–especially late game–as it is almost entirely carried by gear. It’s also flexible; you can go melee or ranged, and there are options in Rogue, Warlock, and Paladin, plus Barbarian and more if you want to get creative.

What Can I Expect?

An enhanced martial build, dual-wielding either melee weapons or hand crossbows. 40+ damage per single action at level 6 isn’t unusual. It’s a luck-oriented build, but it will get more consistent as you gear up, culminating in a killing machine that can single-handedly clear whole encounters when on a streak. Like any Fighter build, it won’t be exciting before level 5, and even less so in the Champion subclass. It won’t take long to start stacking dice, but you’ll be stuck at 19-20 for crits until late Act 1. You’re not exactly bringing a lot of party utility, either. Critting face is your utility.

Multiclass Builds

Here are some builds in recommended order:

1. 5 Fighter (Champion) / 1 Warlock (Great Old One) - the best option to start if you’d rather keep the same build all run. It’s just pure unga bunga until level 6, at which point you get Hex for longer fights (and as a combo with Strange Conduit Ring). Champion expands your crit range, and Great Old One gives the Mortal Reminder passive, which even works on ranged attacks.
2. 5 Fighter (Champion) / 5 Warlock (Great Old One, Pact of the Blade) / 2 Paladin (any) - one possible continuation. You get an extra swing from Pact of the Blade and access to Divine Smite, which will use level 3 Warlock slots to add 8d8 on crit, rechargeable on short rest! Warlock has some nice out-of-combat bonuses for avatars, too.
3. 5 Fighter (Champion) / 1 Warlock (Great Old One) / 3+ Rogue (Thief) - another option, this time getting the extra swing from Thief (not much difference between main and offhand in this build). Good if you want access to Rogue skills, and Sneak Attack is a nice pile of damage on crit. Hex and Mortal Reminder are worth the dip into Warlock.

Ability Scores

Generally speaking, the starting priorities are:

STR or DEX to 16 > CON = WIS > CHA > STR = DEX > INT

16 in your attack score raises your damage output floor, especially early on in the game. STR gives you more melee weapon options, but DEX is necessary if you go hand crossbows and it’s better defensively. You’ll never need more than 16 either way, and once this build gets rolling, you might even opt to move some points out if you’re the min/max type. Defensive scores are good for this build, and CHA also helps with Mortal Reminder’s DC.

Gear

The gear that expands your critical threat range is:

• Weapons: Knife of the Undermountain King, Bloodthirst, The Dead Shot
• Armor: Covert Cowl/Dark Justiciar Helmet/Sarevok’s Horned Helmet, Shade-Slayer Cloak (only while Hiding)
• Elixir: Elixir of Viciousness

Other key pieces:

• Risky Ring: Advantage is what makes this build work. Not available until the start of Act 2 unfortunately, but until then, use tactical gameplay or things like Gandrel’s Aspiration against Monstrosities, for example. Risky Ring can be combined with Amulet of the Harpers to offset the debuff if you’re anticipating trouble. Gloves of the Growling Underdog (mid-to-late Act 1) are a fine substitute until you can get your hands on the ring.
• Broodmother’s Revenge: generally best in slot for a crit build, and you can get it super early. This doesn’t work like regular poisons, as it’s carried on the weapon attack directly (and thus eligible for double dice on a crit). Catch is that it has to be enabled, preferably by a support character or a Goodberry/weak potion before combat.
• Strange Conduit Ring: combos with Hex, as mentioned above. While Hex alone may not be worth the action on short fights, the concentration is permanent until you get interrupted. I’ve frequently had this up all day from a single Hex cast.
• Disintegrating Night Walkers: can’t crit faces if you can’t get to your target. On top of the excellent mobility, it also covers some common Saving Throws when wearing Risky Ring.

Beyond this, you’re looking for anything that adds dice (not flat damage!) on regular weapon attacks or otherwise leverages crits. Examples are Intransigent Warhammer, Sword of Life Stealing, Handmaiden’s Mace, Hammer of the Just, Flawed Helldusk Gloves, and Shadow-Cloaked Ring. Also note that Bow of the Banshee will tack on an extra die to melee attacks against targets you’ve frightened with Mortal Reminder (a nice stand-in for The Dead Shot until you get your hands on it).

Tadpole Abilities

A use for Psionic Overload! Like Hex, this will double dip on things like Sneak Attack. As a general rule of thumb, I’ll turn this on if I know I’ll have three more rounds in a fight or if I can’t get in range. Note that this is a bit of a nonbo with Hex in that it will trigger additional Concentration checks. An item with Magical Plate, like Adamantine Splint Armour, will negate half of these checks.

Luck of the Far Realms is an obvious choice. Also, since you’ll be rolling Concentration, Concentrated Blast is always an option if you ever need guaranteed damage in a tight spot.

Feats and Support

For feats:

• Savage Attacker is absolutely essential if you don’t have Knife of the Undermountain King on (though even if you do, there’s still a diminished benefit). It rerolls almost all of your dice, and this is a dice-stacking build, after all.

• Resilient: Wisdom is important. Can’t crit faces if you’re in Hold Person. Better than just tacking on points to Wisdom.

• Sentinel, Mage Slayer: interesting choices as opportunity/reaction attacks hit like a truck with this build.

• Sharpshooter, Dual Wielder: conditional feats. Sharpshooter is good if you’re running hand crossbows, and the penalty is mitigated by having Advantage up all the time. Dual Wielder will open you up to a lot more melee weapons, though this build can do just fine with Light weapons.

This build shines with a support. Phalar Aluve: Shriek adds a ton of damage, as not only is it an extra damage die, it allows Hex and Psionic Overload to double and even triple dip. All subject to doubling. Haste, Warding Bond, Enlarge, Crusader’s Mantle, and Heroes’ Feast are all highly desirable buffs for this build.

Go Forth and Crit

Quaff an Elixir of Viciousness (Bloodlust and Colossus are alternatives if you don’t have one yet), turn on Broodmother’s Revenge with a heal, Hex if you’re not already concentrating, and swing away. Throw up Psionic Overload for longer fights and apply Hex to big targets. Enjoy the pile of numbers!

Edit: edited to add Gloves of the Growling Underdog, Bow of the Banshee.