Whenever you recharge a card it is from your hand. I will add unless something instructs you to do otherwise. (Like a cure spell or something that specifically says recharge from your discard pile).
I've been confused. Lem's ability states I can recharge a card to add a bonus to a check, however I don't know if that's from the discard pile or the hand. I checked the rules and it was vague. Can someone explain?
Generally you play cards from your hand, whether that's reveal, display, discard, recharge, bury, or banish. Otherwise the card or power says, for instance, recharge a card from your discard.
For reference, here is where to find this in the rulebooks.
If you are instructed to play, reveal, display, discard, recharge, bury, banish, or otherwise manipulate a card, that card must come from your hand unless otherwise specified.
If you are instructed to play, reveal, display, discard, recharge, bury, banish, or otherwise manipulate a card, that card must come from your hand unless otherwise specified.
Good luck on your adventure.