Once you enter the hub, slide down the vines to get the land ahead. From here you have access to the first three levels. You will need to collect two more treasure keys to gain access to the Ghost Production Facility.
To access "The Lair of the Beast," jump on a trampoline and slide on a vine. To access "A Grave Undertaking," jump on the trampoline with two candles, and climb onto a rope, then sneak around the ledge to get past the water rat guard. To access "Piranha Lake," go below where "A Grave Undertaking" is and climb shimmy across a pole.
After gaining enough treasure keys, head to the gate on the far corner to unlock it. The Beast will appear and break open the gate to the facility. Head through the gate, then you will come across the heavily guarded voodoo egg beater. To access the remaining levels, all you need to do is sneak around the machine on a root, dodging the guards' flashlights.
After gaining the remaining keys, walk onto the platform above the voodoo egg beater to unlock it and take out the guards. Hop onto the lid to launch yourself up to the Skull Temple to take on Mz. Ruby.
- On the walkway above is a forcefield that can be deactivated from the other side by destroying the candles.