"Sword damage -1, Sometimes deadly"
When equipped, the Whimsical Ring will have a random effect on Link's sword power. On most sword slashes, it will only do one unit of damage (for comparison, the Wooden Sword normally does two units of damage). However, there is a 1 out of 256 chance that there will be a deadly strike, instantly killing the enemy.
Given the incredibly low success rate, the Whimsical Ring is not advised as a ring to be worn. There are other power based rings that are more valuable when equipped, in particular the Power Ring L-1 or the rare Red Ring.