In the game "Final Fantasy 7," the Cursed Ring is considered to be one of the best and the worst items in the game. This is because it massively increases the stats of the character that wears it. However, it also puts an effect called "Death Sentence" on that character at the beginning of every battle, which will cast the instantaneous Death spell after 60 seconds. Fortunately, there is a way to wear the Cursed Ring without being subject to the Death Sentence. It can be countered with a "Destruct" materia and an "Added Effect" materia.
Go right from the cave entrance of the Cave of the Gi. You will see breakable rocks at the cave entrance.
Break the top left rock to find a door that leads to the next section.
Enter the door and go right and down the ladder to reach a ledge with the Added Effect materia on it. This materia is not buyable in shops so you must find it here.
Check all the houses in Nibelheim and go to the mansion in the north end of town.
Go down the spiral stairs into the basement. There you will meet Sephiroth, who hits you on the head with a Destruct materia during a cutscene. Pick up the materia after he leaves.
Equip the Added Effect and Destruct materia on a character that you use often. This is to level the Destruct materia, since fighting with the Destruct materia equipped will allow you to reach Master level with it. A Master-level Destruct materia allows its user to cast the "Death" spell, which has a chance to kill the opponent instantly. This will be very important for the next step.
Place your Master-level Destruct materia and your Added Effect materia into an armor piece with two linked materia slots. It's very important that it is an armor piece and not a weapon because when the Destruct materia and the Added Effect materia are linked by placing them into an armor with two linked materia slots, the Added Effect materia will cause the armor to protect you from the effects of the Destruct materia. This is also why you want to use a Master-level Destruct materia that can cast "Death," as the Added Effect materia and the armor will make you immune to all Death spells, including the one cast by the Cursed Ring's "Death Sentence."