Tartarus
Follow the path and about midway through Kratos should fall upon a chest containing a Phoenix Feather inside. Round the bend to a ring-like area, at which point a Centaur makes an entrance and dozens upon dozens of other minions join the skirmish. The lesser minions serve as great Battering Rams, whereas the Centaur itself shouldn't be too difficult to deal with if you repeatedly spam Hyperion Ram or use the Nemean Cestus. After the dust settles, hop up and proceed to the next area.
Gates of Tisiphone
The next area features a bit more of a challenge, where Kratos is pitted against two Chimera. The second one appears a bit later--around the time the first Chimera sheds its first form. Keep the strategy simple: focus on one at a time, although if the opportunity presents itself don't shy away from peeling off the multiple layers of the other Chimera. We found that the second Chimera presented the least issues when it remained in its first, serpent form mostly because it didn't pounce around or charge as much. Utilize the great number of oil cans scattered around to inflict major damage upon the wretched abominations too.
Afterwards, yank both chains here to re-arrange pieces of the wall, and then push the two blocks into the wall. Jump up the left side and lasso the hapless Harpy. Steer it toward the blocks on the right--these slide in and out of the wall in a readable pattern. Just land on the unmoving platform and then jump up to the blocks when they slide back out. Make your way up this wall, utilizing the Harpies and some nice timing to eventually reach the very top. Turn this engraving to bust open these giant doors. Save your game and dive into the Pit of Tartarus.
