The best magic is that of Haven:)
As it was said: "if the enemy cannot get close enough to attack, they won't be able to attack. Simple physics."
And meanwhile, you hit enemies with spells and shots:) Sieging is generally elementary - displacement removes archers from the towers; if they climb up, they get a bolt from the djinns and another displacement from the hero; mages poison everyone alive, and the djinns spend their free turns creating illusions:)
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