This level is nuts. Where is the Oscuro key? I don't see any youtube videos on it or anything. I found the other 3 and the secret switch behind the fire wall you race but I can't seem to find anything else to even do.

Yeah this level is overcomplicated.

Well you can use cheats like no clip (code: spispopd) or reveal map (code: cartier) to see where are all the things. I found where oscuro key is that way, but still did not properly crack the level. Too many pushwalls that "appears to be locked" wth touchplaces somewhere.

It's definitely very hidden. The switch to move the wall hiding the oscuro key is in the same general area that the key itself is in. Notice that GAD moving back and forth? It goes through 2 structures in its path. Press along the right wall of the second structure to find a secret area with a switch that opens the wall hiding the oscuro key.