The Dream Card can literally destroy the mind if it shows the victim their dreams, whether they are good, bad, or frightening. It takes on various forms, which include it's human like form, and that of a butterfly.
In Episode 40, the group visits the Radio Tower, where they are all attacked by Dream. Sakura is shown the premonition like dreams she has been having for a long time. Li rescued her by using Time . Sakura quickly recovers and seals Dream, which goes to Li before he passes out. When used as a card, Dream shows the person it's being used against they're dreams.
