I have been a very active poster these last few days, but the Warhammer setting is one of my favorites. In Warhammer Fantasy Battles, primarily the Beastmen Armybook mentions a race of beings the Dragon Ogres that existed on the world before the arrival of the Old Ones who made pacts with the Dark Gods. As they age they grow larger and more powerful being that they are immortal they will only die in combat. But my idea to include them into the Warhammer 40k RP is that on a distant world before the War in Heaven a species that was just as psychic as the Old Ones though lacking in technology they remained on their own world fighting amongst each other for territory and mates. When the Empyrean was thrown into Chaos the Dragon Ogres were effected greatly. And as that time flows differently in the Warp they contacted the entities that would eventually become the Dark Gods.
Those pacts granted the Dragon Ogres immortality and ever more power but they had not left their home world. That changed when Horus betrayed the Emperor and looked for allies in the stars. It was the gods that lead Horus to the storm ravaged world the Dragon Ogres call home. The youngest of them could battle the tanks with the eldest of them being able to stand against even the mighty titans. They were brutally effective weapons against the armies of the Emperor and thousands died beneath their claws and psychic power. But not even their added power would allow Horus to win the day. After the siege of Terra ended the armies of Horus fled and on many worlds the Dragon Ogres where left to bare the brunt of Imperial retribution and many of them died.
Some learned to travel the Warp and move between worlds and the survivors began their dark exile. Many began to search for their lost home world. Others chose to sleep beneath the rock waiting for the proper champions to bear the marks of chaos will awaken them allowing them to serve. For anyone or anything else they will not.
In game terms I am thinking that the PCs would each to need to carry a mark in order for the Dragon Ogre to rise. I may end up dividing them into three board groups. The smallest being able to take on a tank so it can act as a transport and carry weapons. Next size up could battle a Warhound Titan or a Super Heavy, this would be more of a set piece ally. The same would be true with the eldest stage that could battle a Warlord titan and smash down Hive cities. Has anyone done this before and can offer advice? Or even if you haven't opinions and idea's to flesh the idea out further?