Hades was locked into the Underworld

This gave him time to think about his revenge

To rejoin the bridge, he would need the power of 5 gods

And here appears the contracts...

Hades gets the power of the souls in Hell

And to get a power capable of joining the bridge, needed more dead in hell

Besides the evil souls that were destined to hell ...

Hades was obtaining that everyday dozens of good people will sign the contract, and thus get many more souls... and power.

He already got enough power to join the chain.

That's why all this riffraff is here, watching to see what happens.

Riffraff?

WTF?!

After class I wait you in the gym

Moron!