The bonus of the Illusionist gives +20% to the hero's Illusion spells.
The Illusionist is most likely to learn Tactics and Order Magic and fairly likely to learn the Scouting, Life Magic and Death Magic skills. Illusionists can not learn Chaos magic or Nature Magic when leveling up unless some basic training in those skills is already known.
The class bonus is similar to the Enchanter's bonus, but without the increase to Summoning spells (since Order magic has no such spells).
Illusion is of some tactical importance, so this is not a bad bonus, but not at all a great one, either.
|Heroes of Might and Magic IV classes|
|Standard hero classes||Knight - Death Knight - Lord - Thief - Archer - Barbarian - Priest - Necromancer - Mage - Sorcerer - Druid|
|Advanced classes||Archmage - Assassin - Bard - Battle mage - Beast lord - Beastmaster - Cardinal - Crusader - Dark Lord - Dark Priest - Demonologist - Enchanter - Field marshal - Fire diviner - Fireguard - General - Guildmaster - Heretic - Illusionist - Lich - Lord commander - Monk - Ninja - Paladin - Prophet - Pyromancer - Ranger - Reaver - Seer - Shadow mage - Summoner - Warden - Warlock - Warlord - Witch king - Wizard - Wizard King|