Warhammer 40,000: Dawn of War/All Out War

The final mission is a kind of a tactical anticlimax, being bafflingly easy. Your only objective is to kill the Daemon Prince. This is actually even possible with the force you start with, but this guide will primarily focus on the more conventional way.

First of all, you want to be somewhat aggressive/expansive from the start, but not quite as much as in the previous mission. You will often run into Possessed Squads, so sending single squads to take points is risky. If you take 2 squads and a vehicle or commander, on the other hand, you can usually defeat even a larger force quite easily.

In the beginning you have some Possessed right on your doorstep so get rid of them (dance with your Marines) and get the nearest SPs. Anytime you expand, you need a basic defense for your SPs because of Horrors spawning from the pits all over the map. You should be able to expand both left and right from the start; you want the left side because of the Relic and a Chaos base in the far corner, and the right side if you want to keep the Eldar alive. Making a "chain" of fortified LPs up their way makes it easy to throw some mobile units (a Land Speeder, an Assaut Marine Squad) to bolster their defense.