The Messiah's goal is to act as a leader to the Team of Heaven and to guard Heaven's Gate, the Citadel, and ultimately, God's Throne. The Messiah has a lot of roles to play as well.
The player needs to focus on having Predators nearby to counter Mammon Rushes, keep Sandophalon alive to absorb Tormented Soul hits, keep Duma alive to Forcefield Abaddon to kill her, keep Messiah alive to kill Asmodeus' Hellfire, and keep Chariots alive to demolish anything menacing that flies in the sky.
Early on, White has to defend the middle lane. The Devil will try to burst through the Pearly Gates using a multitude of tactics. He could simply send the Devil to destroy the gates, or he can Dark Swarm and then send in Mammon, or his Tormented Souls to demolish everything.
If the Devil comes alone, simply shoot him down with Duma, Messiah, and the nearby Chariots.
If Beelzebub decided to Dark Swarm, put Sandalphon in front of Heaven's Gate, he will absorb all of the Tormented souls, and can take a few hits from Mammon. Be sure to push mammon into a wall before killing him with the Predators.
Note: Zadkiel should be with you to kill the Eggs from the Dark Swarm.
If you can manage to kill Mammon, congratulations, the massive brute is now dead, and the Devil's ability to push will be significantly lowered.
Go ahead and help out on the right side, usually the Asta Ball will be killing off tanks.
If Duma can forcefield Abadon into a trap, and kill Abaddon, then Astaroth will be hard pressed to do too much again Heaven's forces.
Warning: During this stage of the game, The Devil might try to kill Benediction with his Harpies. To prevent this, you can put all extra Angels directly left of the Benediction. This will prevent the Harpies from doing any damage.
After Heaven's Gate has fallen, stay around until all the cannons around Heaven's gate have died. Sometimes, The Devil just tries to kill Heaven's Gate hoping that the forces of Heaven will retreat, letting him then destroy the cannons without an issue.
In the midgame, have Duma with the Saints. The Saints are wonderful, they can do ranged or melee damage. Make sure Duma's shield is on. At this point, it is helpful to know how to block paths. You can select Predators and have them cloak and hold position. The only way Hell can see these Predators is if they Fungal, Plague, or spot them with Grigoris. If Seraphiel has been killing off Grigoris with you, then this shouldn't be too big of a problem.
Encourage Zadkiel to stay in the middle lane with you, to kill off Beelzebub's eggs, but if he wishes to go elsewhere, let him.
Asmodeus' Hellfires will be raining destruction upon Seraphiel and Uriel's forces, so have Messiah try to kill these tanks off, however, be careful of Asmodeus' crazy anti-air fire, along with Abaddon's Fungal and Harpies and Gargoyles. The Messiah can die.
When it comes down to it, it is more important to protect the Benediction than it is to protect the Citadel, so do not be afraid of abaddoning the Citadel in favor of protecting the Benediction.
Eventually, even the best of teams will lose all three buildings in the middle. Welcome to the Late Game.
The Late Game compromises of holding out until God comes. You will lose units. You will lose heroes. It is worth it to hold out just 30 seconds longer.
Units that can heal (Raphael, Donatello) and Duma's Shield is amazing here. In fact, Duma is amazing. He can Force Field to prevent units from streaming into the Throne.
Try to encourage Raphael, Donatello, Jeheol, and Zadkiel to go out and kill Nyduses. If a Nydus falls, Hell has to rebuild it, subtracting precious seconds from the timer until God comes.
Try to get your team to kill off Hell's creep too, if you can. Once God comes, you don't want Hell to be able to counter-attack the Throne.
Late Late GameEdit
God has come! It is game over, or is it?
God is a mothership, and he can die. Be careful with him, Asmodeus' Anti Air is very heavy, and Astaroth's Poison can wittle down God's life. If Beelzebub is alive, Dark Swarm will make your life miserable. If Sammy is alive, Asmodeus can kite you endlessly.
You MUST protect your flanks too. Have some of your team stay back to protect the Throne. Even though God is awake, if the Throne dies, Heaven loses the game.
Now, to win, kill the three Prime Evils! You can also kill their Gate to Hell, which will drain the life of the Prime Evil, and prevent them from getting elites, along with not allowing them to remake their Nyduses.
God is Dead Late GameEdit
That's it. You dun-goofed. The only thing you can hope for is that Hell will make a mistake and kill their remaining Prime Evils.