A creature named Kyubey offers to grant Madoka a wish if she becomes a 'magical girl' and fights grotesque witches. A magical girl named Homura tries to stop this agreement, and the true nature of the contract with Kyubey is revealed.
Did You Know?
Each of the six main characters has a musical leitmotif that relates to their character arc: Madoka has Sagitta Luminis (Arrow of Light), Sayaka has Conturbatio (Disorder) and later Decretum (Decision) (same motif, different arrangements), Mami has Credens Justitiam (Believing in Justice), Homura has Puella in Somnio (The Girl in the Dream), Kyoko has Anima Mala (Evil Soul), and Kyubey has Sis Puella Magica (You should be a Magical Girl). See more
When Kyubey explains entropy, he says it involves the net loss of energy, which is not possible in physics. What the term actually describes is the decay of energy to its base form - which is heat - and its subsequent scattering through space, until the system reaches equilibrium, at which point all energy conversion ceases until further external energy input. See more
Referenced in Phantasy Star Online 2