GATES OF TISIPHONE
You will see a massive gate as you go inside the Gates of Tisiphone. A chimera will attack you.
After killing one Chimera, another two will spawn. Stay out of the Chimera’s poison as much as possible in its first form.
With the Chimeras dead, open the chests that are here. To each side to your north, you should see a glowing chain. Pull it down and it will start the process in opening the gate to the Pit.
The blocks of the gate will start moving. Push the two blocks that are shinning and start your way up.
Use the Harpies in this area to help yourself go up to the platform.
Once you’re up, open the Gates to the Pit of Tartarus!
Before proceeding through the Pit, use the Save Point and open the treasure chest that contains a Phoenix Feather.