Black Throne CPT 3

[Maranatha666]

So, this Area sucks. Too difficult, just as you thought yeah i done it they slap u in the face with another brain cracking Challenge...

Here´s my question, hope someone can help:

When u have to activate the 3rd Beam, u can throw this explosive trough a portal and then a platform rises halfway up. But after that; what should i do? i cant reach the upper zone cos this platform isn´t high enough and i dont know were i can find this stupid key for the locked door that i still need! Does someone know what to do?