I was trying to find a star cloak from a mimic to combine with a cross necklace. Everytime I killed a mimic, I would either get a cross necklace, a magic dagger, or a compass. Every single time. This was going on for a couple hours, too. To make things worse, I couldn't find mimics for the life of me. A common tip is to run around in Hell across a bridge to find shadow chest mimics, but I only found 3 in the huge amount of time I looked down there. After that I was searching in the Underground Hallow and Underground Crimson and found several there, but they all gave me cross necklaces, magic daggers, and compasses, like I said before.
I finally had enough and went to bed. Next day I was playing, the first mimic I found dropped a star cloak.