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Which of the heroes possesses which magic (or is it in their stats?)

Actually, it's indicated there.

But to reiterate: initially, the magic of Growth belongs to the Prophet, the Wizard, the Sisters of Light and Darkness, the Abbess, Master Rala, Mord-Sid, the Seeker, the Confessor, the Witch, Mrisviz, and the Snooper. The magic of Damage initially belongs to the Snooper, the Sister of Darkness, Mrisviz, and Master Rala. The Confessor gains it after meeting the Seeker, and Mord-Sid gains it by capturing the magic from anyone who possesses the magic of Damage.