This might actually beat the Owlbear elbow-drop as Baldur's Gate 3's most creative kill, utilising a decidedly mid magic item to deal hundreds of damage, taxing a central villain so hard they just die.
This hairbrained strat comes from GoldenThane, who posted their kill to the Baldur's Gate 3 subreddit yesterday. The Twist of Fortune mace—which you pick up from the Tolltaker boss in the same Act—is an economic equaliser with a special action called "Blood Money", which deals an extra 3 piercing damage per 300 gold your victim is holding.
Usually, this doesn't do much. Some targets might have a few grand kicking around for a nice damage bonus, but it's hard to glean someone's wealth when you're already in a brawl with them. It's also a once per short rest ability, so it's not like you can keep fishing for gold.
If you have a lot of disposable income kicking around, however, you can launder your wealth into the pocket of most characters by reverse-pickpocketing them. This is especially funny when you consider that 15,000 gold weighs 15kg in game, which is a lot of weight to subtly add to someone's bags—the best part is that it doesn't even require a skill check like taking something out of their pockets does. Maybe Thorm just really needed the money for Isobel's college fund.
While the damage numbers aren't that impressive on screen, that's 50 instances of three damage for a meaty 150 smack. Hilariously enough, the Illithid passive "Cull the Weak" triggers for each separate application from the toll taker, adding a whopping 50d4 (50-200) psychic damage on top.
As user Spedwards points out, the implications of this are dangerous. You could hypothetically equip other items that apply damage like Cull the Weak to nuke anything above a certain income level. I myself wonder whether spells like Hex or Hunter's Mark (which add an extra 1d6 to weapon attacks) would work the same way—an extra 50 to 300 damage isn't too shabby for a 1st level spell slot.
This calculation is a double edged sword, unfortunately. Ketheric himself is wearing armour that reduces all incoming damage taken by two—which applies to each separate damage instance individually. This meant that GoldenThane had to plant the 15,000 gold seed early, beat the first encounter with Ketheric fair and square, pursue him into the underbelly of Moonrise Towers, then force him to enter his second phase as the Apostle of Myrkul—which still had the 15,000 gold in its pockets, despite being a horrifying skeleton thing.
User srsbsnsman did try to see if you could cut all of the running around by dumping 50,000 gold into Ketheric's pockets and one-shotting him through that damage resistance, leading to a 'truer' one shot. This just wound up bugging the poor guy out, soft-locking the game.
PC Gamer's own Robin Valentine recently pointed out how playing the game is like contending with an eccentric DM, and this very much tracks with that assessment. Once again, I find myself filled with a strange kind of tabletop patriotism at the sight of these weird power gamer interactions. It's basically a rite of passage for any fledgling DM running a Dungeons & Dragons game to give players an innocent magic item, only for them to pull off a hairbrained scheme with it. Typically, that's something like an Immovable Rod—here, it's a mace that collects taxes.
Unless Larian Studios decide to patch how these items trigger off the back of Blood Money, though, I'm just delighted that there's a genuine build one can make around the Twist of Fortune. Hypothetically, you could one-shot anything rich enough—only once per short rest, unfortunately, money can't solve all of your problems. In this case, though, it's worth its weight in gold.