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. You can game this by shuffling yourself first, so that it unshuffles you.

Darkest dungeon antiquarian useless