From Dark and Darker Wiki
higher luck higher chance max at 0.87%, see loot table chard of treasure hoard in hr with 500 luck. every time you finish interact with it, it roll 1 time at a base chance of 0.1% in 0 luck, 0.87% in 500 luck. other than goblin cave and 1st floor of ice cave which is 0.03% at 0 luck, 0.26% at 500 luck.