Warcraft III: Reign of Chaos/Key of the Three Moons

Mission Objectives
🇨🇴
 * Main Quest - Three Moons
 * Destroy the three High Elf Altars
 * Collect all three Mooncrystals

🇨🇴
 * Main Quest - Gates of Silvermoon
 * Bring Arthas to the Gate

🇨🇴

Starting Units
You start out with Arthas, 4 Ghouls, 2 Necromancers, 1 Meat Wagon, and 4 Acolytes, soon joined by 3 Crypt Fiends. With no structures, you're also way past your food limit.

Strategy
When you've acquired the Crypt Fiends at the beginning of the level, clear out the High Elves at the gold mine to your southeast. Establish a base there.

Getting Started
Priority one is building up clusters of Ziggurats - you're over your food limit - and a Graveyard to upgrade them into Spirit Towers.

Skip over the Crypt, unless you need more Ghouls. Get a Halls of the Dead for a Slaughterhouse and a Temple of the Damned, for extra Meat Wagons and to upgrade your Skeleton Warriors.

Defense
Sylvanas's base sends out complete groups of infantry across the bridge. The other major base mainly sends out Windriders to attack from your north. Assault power and size increase over time, but frequency lightens up as you crush their bases.

Leave a thick layer of Ziggurats to your north and west, backed up with some Crypt Fiends and Meat Wagons against Sylvanas.

Altar One
When you're ready, take the Zeppelins from the Goblin Laboratory and cross the river east to the rune symbols. You should have Arthas, 4 Necromancers, 2 Meat Wagons, and whatever Ghouls and Crypt Fiends you want as backup. Keep Raise Dead on Autocast.

Take the Gold Mine, you'll need it. The Way Gate here leads to the central island. If you're not worn down, go through and cut through the Elven outpost there.

Altar Two
Go through the middle Way Gate on the central island.

6 Necromancers and 4 Meat Wagons are recommended; if you're all upgraded, the Skeleton Warriors make all the difference.

Keep in mind that you can ignore the Sky-Fury towers, which are anti-air only.

Altar Three
Sylvanas's base is through the last Way Gate on the central island. This guards the last Mooncrystal key.

To the Inner Gate
Bring Arthas to the Circle of Power in the northeast, ignoring the defenses.

Summary
The Necrowagon strategy works well in the High Elf levels. You'll need a crew of Necromancers summoning Skeleton Warriors from Meat Wagons packed with corpses. Bolstered with Crypt Fiends, it's your best shot.

The first Altar is to the east, via Goblin Zeppelin. The Way Gate here leads to the central island; the central gate leads to the second Altar, and the left Way Gate leads to the final Altar under Sylvanas's defense.

Expansion locations are at the first Altar, the central island, and the second Altar.

When the Three Keys are pieced together, take a Zeppelin and drop off Arthas and anyone else at the Inner Gate. Mission ends when Arthas steps into the Circle of Power.