At level 70, there's a whole bunch of things to do to keep yourself entertained. Way more things to do than used to be the case at level 60, in fact.
Daily Dungeon quests are one of the many dailies a level 70 player can get involved with, and each day there are two daily dungeon quests - one for a dungeon on regular mode, and one for a dungeon on Heroic mode. The %26#8220;regular mode%26#8221; daily dungeon quest can be done in Heroic or Regular and count, whereas the one requiring Heroic mode cannot be done on Normal mode.
Generally, the reward for completing a Heroic mode Daily Dungeon quest is a chunk of pocket change (ie: nearly 25g) and two Badge of Justice (which can be turned in for nice epic gear when enough are accumulated).
The reward for the regular mode daily dungeon quest is slightly less pocket change (8g 80s) and one of these Ethereum Prison Keys.
A Place To Use Your Ethereum Prison Key For Lewts And Rewards
I think there's a few things you can do with your key, but I went for the easiest-to-solo option, which was to fly to Netherstorm and find a specific spot (54,40) that had a bunch of Ethereum Prisons on the ground in their pink bubbly format, and use my keys to unlock the prisons and free that which was inside.
From what I had read about it, the keys would unlock the bubble and either a %26#8220;friendly%26#8221; or an %26#8220;aggressive%26#8221; target would emerge. The aggressive ones would require killing but would drop loot of uncommon and higher quality. The friendly ones... I don't remember. The first four keys I turned in gave me Aggressive targets to kill and loot.
Have you used your keys for other things?