According to Ravensburger, they are much rarer than the Enchanted cards (which is as astounding considering finding an Enchanted card is about 1 in 1,200 cards)
Your opponent may not leave exerted characters out for him, or only exert characters with high willpower but there are workarounds
These are cards that cannot be put into your own deck , and they are only used in the Illumineer's Quest Deep Trouble to defeat Ursula from taking over Lorcana
Tellah, Great Sage A useful way to evaluate cards is to consider what similar effects cost, and whether you get a discount on the ability
Dont Ink, or Mulligan, The Queen, Commanding Presence if shes in your opening hand Grumpy, Bad-Tempered gives all Dwarfs plus-one power
At just four Ink, Belle comes down quickly, letting you play an extra card into your inkwell on your turn