Covenant explanation?

The Covenant for the Angels was changed it seems, although, I've yet to find a detailed description on how it develops. It used to be really simple to figure out with angels having to attain certain levels, etc. Now, it is totally different other than the Activation of certain angels for a particular covenant.

So...could someone provide a comprehensive description of the current development/evolution of the various levels of the Angel covenant?

Thank you,

SirDandy at uc21