Spells are divided into three types - unit spells which enhance a single unit, combat spells which are used to directly damage or handicap the enemy during combat, and global spells which can affect terrain, structures and groups of units on the global map, or summon magical creatures to player's aid. All have different mana costs depending on how advanced they are, and some of the more powerful unit and global spells can take more than one turn to cast. Counterspells to block and dispel unit and global enchantments are also available. Each spell furthermore belongs to one of the eight spheres of magic: "Life", "Death", "Air", "Earth", "Fire", "Water", "Cosmos" and "Secret"/"Chaos". Mana, the magical energy required to research and cast spells, is channeled from magic "nodes". Some of those are generic, and provide equal (though small) amount to caster of any sphere. Others are linked to one of the elemental planes, and only channel a specific kind of energy; thus, a Fire node, for example, can only be used by a player who chose the Fire sphere. Heroes with "Spell-Casting" also generate mana, your King/Leader more so than others.