Ring of strength
Version 0.17: This article may not be up to date for the latest stable release of Crawl.
A ±X ring of strength affects the strength of the wearer by X (ranges from +6 to -6). If X is negative, the ring is normally cursed, and it can cause stat zero if you are unable to remove it.
Desirability
Gaining a little more strength rarely ever has a very dramatic effect on your character's performances. It provides a slight increase to your accuracy and damage output, and it allows you to wear armour, kite shields, and tower shields more effectively, but its overall impact is usually pretty negligible. A +5 or +6 strength ring might be a good find for early characters wearing heavy armour or a shield, particularly if they also intend to cast spells, but you'll probably want to replace this with something better eventually.