It is wise for anyone doing the Underground Pass quest to remember to wear their Klank's gauntlets while searching the cages of the Souless. The Souless will bite you when searching the cages. However, if the player is wearing the gauntlets, the player will not take any damage. Searching the cages without wearing the gloves will result in taking damage when being bitten by the Souless.
The dove's skeletal remains are crushed and rubbed in the Doll of Iban obtained earlier in the quest in order to destroy Iban.
The Dove symbolizes Iban's conscience, the innocence he had as a man corrupted by evil. The witch responsible for his return owned a beautiful dove, which she strangled with her own hands to provide the proper "conscience" for the ritual, after blood, body, and shadow.