The drop rate of a dark key from this chest is 1/200. You get 150xp per chest and I was averaging out roughly 150 chests per hour.

I suggest wearing weight reducing armor aka Graceful. Bring a Lockpick, Herb Sack, Gem Bag and Rune Pouch.

3:25 dark chest
4:03 loot from both chests
4:20 clue openings
4:55 total loot

#osrs