Once per turn, you may turn a card with an inkwell symbol from your hand into face-down ink, becoming a resource that you can turn sideways to summon characters You use 60-card decks in Constructed, 40-card decks in Limited, and the official website has an excellent "how to play" section
Daisy Donald's Date is a fairly common pull that costs only one ink to play, forces all opponents to draw prematurely, and can quest for two lore
Another very important thing to note on Merlin Squirrel/Rabbit/Crab/Goat is that they say, when he leaves play, meaning its triggered whether the card is returned to your hand, banished, sent to your ink well, or even shuffled back into your deck
These cards work well with Chernabog Evildoer and Lilo Escape Artist, and open up the reanimator deck archetype
If you play her on turn 5 while going first, that shuts down a huge amount of the big 5-cost songs being played cheap