I'm surprised that no one has posted a review on this card yet, so I'm filling the gap here. It is a card that can be interesting in scenarios where the Doom keyword is frequent, or in decks without native or good sphere for resources acceleration. As a 1-cost neutral attachement, it is easy to enter potentially any deck. But above all it is an auto-include card in any deck with Gríma or Saruman.

In the first case, the mini combo Grima + Keys of Orthanc is a fabulous indirect universal resource generator, likely to accelerate the setup of the entire deck, because Grima's action is not limited neither to a type of card, nor to a sphere, nor even to a given phase. Keys of Orthanc increases the effectiveness of an already very powerful and flexible buit-in ability. Concretely, when you combine the Grima action with the Keys, a card that should have cost you 2 will be fully refunded to you after exhausting the Keys. And a card that costs 1 will earn you 1 in net balance. It's simple and terribly effective, if your threat level is not really a big issue in your game.

In the second case, a Saruman deck happily accommodates Keys of Orthanc, as a sort of doomed/Isengard equivalent of Steward of Gondor. It is a card which allows you to underline the Doom theme and which financially supports the dynamics of playing doomed cards, readying of Saruman and drawing when you add Steward of Orthanc to the deck.