I have optimized a character that I call the "Shield Warrior" that I feel is incredibly overpowered in total execution. The character works on all difficulty levels and is somewhat the backbone to all of our party configurations. He has changed and adapted over many runs to what he is now, but has existed with several different iterations.

Shield Warrior

Creation Setup - Human (ranger kit to ensure a bow in first box on the boat)

-1 Pyro (haste,peaceofmind)
-1 Scoundrel (chloroform)
-1 Bartering
- Glass Cannon

I start with 1 str and the rest wits so that I can use (bedroll/haste/peace to pick up the deathfog barrel) but this is not a necessary optimization.

Level 2 I pick up a point in Poly.
Level 3 I pick up all skilled up and put another point into Poly and and 1 point into huntsman.
Level 4 Put a point into Scoundrel so you can grab cloak and dagger

Buy, Adrenaline, First Aid, Cloak and Dagger, Medusa, Spread, Chameleon

For further levels put 1 more into Huntsman so you can get Tactical Retreat and put the rest into Warfare

Add Ifan to the party and steal his OP bow at level 4 or 5. Use bow for the entire first island. If you want to grab Huntsman abilities you can pick what you prefer.

When you arrive at the 2nd island ditch the bow. You'll never use it again. Sneak into the camp where Saheila is held and get the Shield. You'll need spirit vision and a purging wand. You can do this without any fighting as soon as you get to the second island by talking to the advocate and using persuasion to let meistr siva go.

Use the mask of the shapeshifter to eat the elves brain for the extra bartering point and make sure to buy barter belt and neck. Dig up the barter gloves. All civil points should be in barter and just from exploring you should now have enough levels to have 10 points in barter.

Now you buy Bouncing Shield and Battle Stomp. You'll want to go kill ethiene for her belt and then mordus for your 3rd source point. You'll usually be level 12 at this time just from the exploration and couple kills.

Your Shield Warrior should at this point be fully operational.

1 Pyro (ideally from items)
2 Necro (ideally from items)
2 Huntsman (ideally from items)
2 Poly
10 Warfare
XX Scoundrel (as high as you can after Warfare is done)

Max Wits - any extra points start putting into con - obviously keep barely enough finness/str to use gear.

Make sure you pick up spider legs at level 9. This will normally be the last spell you get. Honorable mention to corpse explosion which is actually very efficient damage.

If you want you can grab living on the edge. Our group bans it so we don't use it.

Consumables

We make lots of love grenades and tremor grenades. We buy lots of scrolls but notable rain scrolls and ice fan scrolls should be held by this character. Often after the first round the mages you have will have dropped the magic armor of multiple enemies. You can rain and then ice fan for a total of 3ap to CC up to 3 enemies. Only use the scrolls don't put points in hydro.

Mind maggot grenades are great. You get like 6 in the game and they are incredibly OP.

Use your weapon as a crit stick and upgrade it on the 3rd island to the 15% crit weapon. You'll never need anything else. Expect around 80% crit rate near end game for your shield throws. Prioritize crit and wits on every piece.

Skin Graft is banned from our runs but obviously if you use skin graft the character is twice as strong. Two shield toss crits on the opening turn will kill anything.

Glass Cannon, All Skilled Up, Savage Sortilege, Picture of Health, What a Rush (replace all skilled up at lvl 14) - Last talent is up to your preference. We try to end our campaigns at as low a level as possible so we sometimes don't get the 5th talent.

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Keep in mind that your 2nd character can have zero initiative and still be 3rd place due to how the round robin system works. This is a huge itemization advantage and so the 2nd character can really focus more on raw stats/crit.

What a rush works really well with Death Wish. It might be considered a bit of abuse buy my shield warrior goes into combat very low in health (MOST times). We are actually banning this behavior going forward in our campaigns as it similar to pre-buffing which we have also banned.

Last note - if you haven't banned teleport and netherswap there is a better version of this character that focuses on gather up enemies on turn one and locking them down with spider goop so that casters can just finish the fight on the first turn.