After the Harrowing - Dealing with the Deck

[Iceheart2112]

So my players have just finished up the Harrowing and have the artifact deck in hand. What should I be worried about? I don't want to deus ex machina the thing away from them but I'm somewhat wary of its powers so I want to be prepared for what they may do. I'm asking for you to help me 'game' out some of its powers and what clever folks may use it for. Any help would be appreciated. Thanks!