Shambler is probably the best boss fight for a Highwayman. The real answer is to NOT have immobile plebs, or to NOT activate the altar if you aren't confident your current team can handle that aspect, like farting around with a LEP who's at risk of being absolutely useless in 50% of positions, with their move-res not being a help. Screwing the order of your party is not a catch-all answer to shuffle. You can game this by shuffling yourself first, so that it unshuffles you. No mere hallway fight is scarier than a prepared human player's brain. Heck, I fight every Shambler on principle, namely: The baddest monster in the dark is ME. Shambler usually gives you top-end loot, like Ancestor's trinkets, Puzzling Trapezohedrons (3.5k each), or tapestries (4k? each). Or you can fight Shambler ASAP, and then use the rest of the (L5 long :) dungeon's fights to heal your stress to 0. Then there's no fight left to heal your stress, so return to hamlet and use town heals.

You can save Shambler's Altar to the end of the dungeon (as the last thing you do).

Then you probably have ~80 stress each by the time you kill the last 2 spores. It's not hard to kill Shambler in round 3-4. Or you can ignore them for 2-3 rounds and focus all damage on the Shambler first. The Shambler will promptly summon new ones, but that sidetracks its attack for 1 round, and the new ones are unbuffed. You can kill the spores to reset their buff state. That means their self-buffs are (gasp) exponential After 3-4 rounds, they're hitting for 20+ damage and stress each. Every time they hit you, they buff themselves, no cap (?). + It hides in positions #c-#d, like any boss. You can boost torch during the fight, but you probably should just kill it sooner instead of goofing off.

You fight in the dark, for bonus monster crits. Shambler, and you'd choose not to risk it with that party. Generally, a party with no move-and-attack skills is weak vs.

Darkest dungeon siren meme