Wearing a ring of adornment modifies charisma. The change in charisma is equal to the ring's enchantment; the enchantment can be altered by charging.
Succubi will steal or ask for rings of adornment ("That <ring> looks pretty. May I have it?" or "The succubus decides she'd like your <ring>, and takes it."). Incubi will ask you to put on a ring of adornment if you're carrying one ("That <ring> looks pretty. Would you wear it for me?" or "The incubus decides you'd look prettier wearing your <ring>, and puts it on your finger."). This happens regardless of the enchantment (positive, negative, or zero) on the ring. Additionally, the ring will be identified.
Dropping a ring of adornment into a sink produces the message, "The faucets flash brightly for a moment."
In the original Rogue, a ring of adornment was usually cursed as it did nothing but take up ring space and cause ring hunger. Similarly, for earlier versions of NetHack, rings of adornment had no effect.