Description: get twelve hidden phoenix feathers - detailed description - where to find those - below.
Realm of Hades
The item is located in a place where you get the bow of Apollo. Before you return to the blocked passage in the cave notice that on the first floor, where you a few moments ago knock the container down, is one more alcove. Open it with the bow and jump gliding above the burning container. You will find there a chest with the phoenix feather.
Judges of the Underworld
Another item is in the cave, after the sequence near the statues of three kings. You can find it in a place where you will have to solve an easy puzzle. When the furnace will be on the fire (the stronger one, after knocking down the container), glide up in the air, lower the bars and sjum on it. In that way, you can open the door to the secret room. Inside, in addition to a large number of demonic hands, you will find the phoenix feather.
Palace of Hades
Another item you'll find in the upper chamber of the palace of Hades. You can get it right after the scene with the Persephone's coffin. First, you have to go to the end of the hall on your left. You will discover there a ladder. Being at the top, you'll find two chests with experience, and one (hidden behind a wall) with the phoenix feather.
Path of Eos
During the Path of Eos you will enter the dark cave. At the beginning of it harpies will attack you. At the other end of that room (where the battle with harpies will take place), there will be a hidden passage (use the head of Helios in order to open it). A bit further you will come across a rope which leads toward the end of the stage. Before you use it, jump down on a hidden shelf. You will find there a chest with experience and the phoenix feather.
The Chain of Balance
During the first level of the flight along the chain, in its final phase, you will come across the sequence of climbing with falling rocks. After the climbing, jump down on the shelf, use the head of Helios in front of you and uncover a hidden chest with the phoenix feather.
After the death of Hermes you will reach an involving-agility-sequence. Make use of the boots in order to climb vertical walls. Being outside the building run up the walls to the top, to the place shown in the left image (in the background will be a characteristic sculpture, illuminated with yellow light). You'll find there a hidden chest with the phoenix feather.
The Flame of Olympus Part 2
Another feather is hidden in the room where you will have to solve the puzzle (with the shattered picture of a sword) and perform a piece of music (a mini game which is a very characteristic part of the game, I'm sure you'll recognize it). In that room, on the left side at the top (after the flight over the hot air) you will find two chests: with the phoenix feather and experience.
The next feather can be found at the end of the Poseidon's Chamber level, after killing the princess (and making through the previously closed bars). On the other side of the bars a cut-scene with the Pandora will be triggered. You will also find there a hidden chest (in order to expose it use the head of Helios) with the phoenix feather.
A very visible chest, almost at the center of the path, at the early stage of Tartarus level. Go along the only possible path, which will take turn into the right after a few meters, and after a while you will hit it (with the phoenix feather).
Gates of Tisiphone
This item can be found behind the gates of Tisiphone (after solving the puzzle). After watching a short cut-scene go through the open gate. Just behind it you will find the light to save the progress of the game and a chest with the phoenix feather.
This item has been hidden in the workshop of Daedalus. To get it, first you have to rise the ballista - just pull the nearby lever. Then run up the wall on the right side and jump to the golden teleporter, so as to find yourself near another lever (time-lever). Use it and go back to the ballista. Now, you just have to shoot the rope into the teleporter in front of you (after opening - in the same way - the blocking bars) and knock down chests to the ground. Inside one of the chests you will find the phoenix feather.
The last feather can be found at the beginning of the Hera's garden. After the first cut-scene go straight. You will find a chest with experience, and another two on the right. On the left hand, you will uncover a hidden chest with the phoenix feather.