Try to get a high positive difference. Protect or destroy the totem or doing a crazy solo. This will be explained later. There are 5 different mage classes in Arcana Mysteria Magica. You can switch them by pressing N by default.
Every class starts the game with different spells and can learn different ones.
Magical resistance protects you from losing much life during magical combat, but it will also slow down your Mana regeneration. You can increase it with eating the blue plants. The purple shields lying on the ground are Mana. Shoot them to make them explode or collect them. Spellcasting needs Mana.