On the level Enemy Lines, the holographic map shows a sphere connected to the Guardian. Does anyone think that this might be a Cryptum? To my knowledge there was no Forerunners on Sanghelios but I could be wrong.
Now I must go find it and see for myself. I am intrigued!
It could be the cryptum that cortana uses on blue team and/or they used the cryptum when the forerunners repopulated the planet after the halo rings firing.