Ring of sustain abilities
Not to be confused with the ring of sustenance.
|This ring protects its wearer from the loss of their strength, dexterity and intelligence.|
The ring of sustain abilities cuts any temporary loss of stats in half, rounding down. Note that most sources of stat loss cause you to lose a single point, so this ring completely negates those (e.g. sickness and the Deterioration mutation).
Note that this does not affect the permanent loss of abilities that might be incurred by mutations.
For a healthy character, this is not worth carrying around. But if you happen to have in in your inventory, you could put it on if you come across a monster capable of draining your stats, or if you get sick.
deep dwarves (who do not regain stats naturally) and mummies (who can only regain stats by waiting or spending a permanent MP) might consider wearing one of these rings all the time, and even for them, a good resistance is usually a better choice, since stat drain is rarely immediately life-threatening.
However, the deterioration mutation makes these rings become far more useful. Level 1 of that mutation is generally just annoying, but at levels 2 and 3, it becomes almost a necessity to wear one of these rings until you can get rid of the mutation. A deep dwarf with any level of deterioration will nearly always want to be wearing a ring of sustain abilities.
Prior to 0.15 you received a cumulative effect for wearing two rings, reducing stat loss by 75%, thus entirely negating all stat damage dealt in increments of 3 or less.