Welcome to Warcraft 3 Extended Edition, a project with the goal of expanding the existing game by adding unused features from the campagin as well as by adding new content of the highest possible quality while trying to keep the game as balanced as it can be.
A big part of Warcraft 3 Extended Edition are the faction changing upgrades. An example is the 'Restoration of Silvermoon' upgrade which is available after upgrading to Keep, building the Arcane Sanctum and summoning the Bloodmage hero.
When researched it gives the Bloodmage 5 bonus inteligence, replaces Paladin with Swordmaster, Archmage with Silvermoon Ranger and also makes the Mountain King permanently unavailable.
Footmen, Riflemen and Knights are replaced with Swordsmen, Archers and Dragonhawk Riders, which are buffed up and get their Reign of Chaos model. Also the Captain is replaced with Blood Elf Lieutenant, an elite unit from Prince Kael's army. He has Spell Steal, Magic immunity, Sword Mastery and Swiftness Aura, which gives nearby friendly units 5% more attack speed and 10% movement speed.
Furthermore, the Workshop is replaced with Elven Workshop, Flying Machines are lost and the Mortar Teams and Siege Engines are replaced with Balistas and Wagons, which can restore mana to nearby units and Drain Mana from enemies.
Holy Plating is replaced with Sword Mastery, which gives Swordsmen and the Lieutenant 15% chance to do 1.75 times the normal damage on an attack and 10% chance to dodge an enemy attack. Long Rifles are replaced with Longbows upgrade, which is self explanatory.
Lastly, The Gryphon Aviary and Gryphons are lost and permanenlty unavailable for the rest of the game.
Note: Certain upgrades have their analogs in the new faction the player gets with a 'Restoration of Silvermoon' type of upgrade. This means that if, for example, Holy Plating is researched before changing your faction, Sword Mastery will automaticaly be researched after the change.