There are a few spells that are available to every leader, regardless of Class or Specialization. Most of these are must-have upgrades or spells at some point in the game, like Basic Seafaring or Disjunction.
Attempts to banish a Summoned unit or unit of Magical Origin by calling upon the powers maintaining it in this world. If it fails, the unit takes 25 damage.
Resurrects the owned Hero that died most recently with full
Note that players who go over the hero cap set in the map parameters (via skills like charm or convert) will be unable to resurrect heroes until the total number of heroes in the empire falls below the maximum number allowed.
When cast, has a chance to remove a hostile Global Enchantment based on its Spell Integrity
This is always available from the start of the game.
To use, select the hostile spell in the Spell Tab of the Empire overview, or in the window of the affected city.
Disjunction is classified as a skill rather than a spell, because it does not appear in the spellbook. It can be cast by clicking the intended target spell in the Empire Overview window, from the Active Spells pane. In the case of City Enchantments, they are also available by clicking the spell's Icon in the affected city. Also, it is shown in the Empire Upgrades section of the spell book.