Some Upgrade cards require that the player “exhaust the Hero”
in order to use a special effect offered by the card. To exhaust
the Hero using the card, simply place a Guild token on top of his
Hero card. That Hero’s card is now exhausted, and so he won’t
be able to use any other special effects that need to “exhaust
the Hero” in order to work until his Hero card is unexhausted.
The Hero card can be unexhausted by using a turn to Rest and
remove all Guild tokens from the Guild’s cards. A Hero with
an exhausted Hero card does not suffer any penalty, he can be
activated normally, moving and attacking as usual. He is just
unable to activate special effects that require him to exhaust his
Hero card. He can still use his natural ability (as long as it doesn’t
require him to exhaust his Hero card)