1st ring:
+1 to spell attack & damage
Once attuned, the ring pushes waves of magical power into the user every 60 seconds.
It is said that a skilled magic user may be capable of bend this power to achieve any intended effect as an action.(Arcana Check DC 15)

Cursed: Cannot be removed unless it is in direct contact with the second ring. Curse effects are only learned by experience.
Attempts to use the ring's power will cause a wild magic surge instead of the intended affect.
Forces the user to sneeze random colored mucus in an abnormally large quantity to expel excess power while projecting the location of the second ring into their mind.
The sneeze uses up an action on every 10th round of combat and breaks concentration
Expelled Magic: during round of combat after sneeze -10 to spell attack & damage instead 

2nd ring: 
Once  attuned, the bearer can no longer fully sneeze. Cannot attune unless 1st ring is attuned. Does not use up an extra attunement slot.
In combat the action is still used up on sneeze attempt but no longer expels magic
.
Cursed: Cannot be removed while wearing the first ring. 
Need to sneeze interval reduces by 6 seconds per hour once both rings are attuned, after 10 hours any user that needs to breath will fall unconcious and the rings will unattune and fall off.

"It has been said that fey siblings play cruel pranks."