Dungeon Cards and Runelord Powers
Some cards, when slotted, do not get discarded after use. Dungeon cards are the most common example of this, but Runelords have the capability to also save slotted cards in their Battlemat after utilizing them to Generate Power.
Dungeon cards - when these special cards are slotted into a player's Battlemat they are simply turned over when used in a turn rather than discarded, but still grant the listed power value to the Hero. They will refresh during the Recover phase, automatically re-slotting into the Battlemat and ready for use the following turn. However, a Dungeon card's special action when activated usually requires it to be discarded from the Battlemat, as listed on the card.
Generate Power - Runelords have a special ability to utilize Relic cards and draw power from them. In this case the card's own power is not used, but instead it is turned over (similar to a Dungeon card) and a power of the type listed on the Runelord's Hero card is generated. This is usually less power than generated by the card directly, however it allows the player to generate free power of a certain type, and still keep the Relic slotted for future turns.