The contract is why the other god is there in the first place but I don't think they ever really explained exactly what it was so now we'll find out.
When the Egypt kept having the wars under seth and to a point where literally everyone fighting for throne like ISIS, hathor, ra in some way or other or preferring hours over seth.
That's when Maat invited jeus' army and had the contract with him. Probably something like fight but don't fight till it ruin Egypt and other stuff that haven't been disclosed at all till now.
Guess we about to know.
(Hope I'm not forgetting or mismatching something but this is pretty much it)
Wait what contract what did I miss