Hidden Knowledge

Hidden Knowledge is a process by which you can sac a face-down card with a non-zero Knowledge Stat as part of paying a cost in order to get a Cost Discount for any cost you are paying (either summoning or activation).

Cost Discount

A Cost Discount X allows you to modify one number that is expressed as a digit on the cost text by X.

So for example, if a cost were to say:

And you have Cost Discount 1; you can change any of the 2s in the cost text to a 1 (or a 3). You CANNOT change the any three costs part, because that is not written in numerical form.

Another example: if a cost says "Sac 1 creature", you can bring that down to zero; but if it says "Sac a creature", you cannot.

Rulings

Some other rules and interactions:

• You can only sac for this purpose face-down cards you control with a > 0 Knowledge Stat;
• You can only affect costs that you are paying, you must do so at the moment you are about to pay for them, but before you start paying any part of the cost;
• You can reduce or increase a number. You can reduce a number to zero but never below;
• The delta change on the number must be <= the value of the Knowledge Stat;
• You can sac multiple cards to affect multiple numbers on the cost, but only one card per number;
• You can change numbers associated with mana, material, Soul, discard, or life costs;
• The Soulrift cost used to open a Dimensional Rift during the Rift Summoning Event cannot be discounted as it is not considered an effect or summoning cost.