The goal of capturing and controlling all obelisks is to create a series of ziggarauts and leaving a group of troops such as abominations and crypt dwellers to protect them.
Lady Vashj's Naga and Kael's blood elves will attack as well, but ultimately illidan and his troops will be your greatest adversaries. The Defenses will be important because not only does illidan strike quickly, he returns to the battlefield quickly as well, you will need to expand you bases to the multiple gold mines across the map to ensure you have plenty of defensive towers to repel enemy attacks. While you attack the units protecting it, make sure your acolytes are building all the essentials for a base, Crypts, Altar, ziggarauts, everything necessary to build defenses and an army. You should be able to capture the closest one to you with the troops you start with. This will help you build gold and lumber while you try and capture the obelisks. Your first goal should be to take your group south of where you start and destroy the naga there to overtake and haunt the mine with your acolytes, starting your own base.
