Together, they return to the cult quarters. "I cannot disagree. I miss seeing the sun in the sky."
Their undead companion, Sokol, does not sleep. But even so, Anton volunteers to stay up for first watch while he works on his journal.
Spoiler: Long Rest
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The party recovers through their long rest, and regains their lost spell slots. Kellon is also able to Attune to magic items, if he wants to.
Time passes slowly, unknowable down in the dark of the dungeon. But one by one, each of them take their turn on watch, and each of them recover from their wounds. The effects of the Shadows' baleful touch fade and Kellon awakes with the strength restored to his limbs.