Melt the hoar frost.

Exploration Stage: Gift Shop
From: Detective
Description: There is some sort of engraving on the ring that’s been found. But I can’t make anything out. The ring is completely covered with hoar frost. Could you bring me a wax candle? It will help us melt the hoar frost and we’ll be able to read the writing on the ring.
Completed: We have the candle, so light it. Right, now be careful, don’t damage the clue. See, the hoar frost has melted. "K. S. + I. L." is written on the ring. Hmm, the situation has not become clearer. I don’t know anyone that lives in the City with the initials "I. L." or "K. S."