On this page of the guide to Immortals Fenyx Rising, there is a map containing the locations of all of the Ambrosia within the region of War's Den.
You can find Ambrosia in 15 places in this region. The resource will be quite easy to obtain in most cases; you will often find the Ambrosia high in the mountains, or right in the open. Some are also found on remote, small islands.
1 - Giant arrows
The Ambrosia is located in the vicinity of a garrison, on top of a nearby hill. The hill is quite easily recognizable due to the fact that there are enormous arrows hammered into the side of the hill, not far from the location of the resource.
2 - Top of a statue
The Ambrosia is located on the highest peak in the region; the peak in question also happens to be a statue which is holding a rock in its hand. You will have to climb all the way to the top, pay close attention to your character's stamina. It is worth stocking up on stamina potions if your maximum stamina is quite low.
3 - Vault entrance
Deep underground, there is a Vault of Tartaros that you can recognize by its red colour. The Ambrosia is located at the bottom. You can use your wings to "dive" to its location. You will also find a few blue mushrooms in the vicinity of the Ambrosia, which will help you get out of the Vault.
4 - Northern edge of the region
The Ambrosia can be found in the northern parts of the region, one of the larger hills is located there. You will find the Ambrosia right at the top of the aforementioned hill.
5 - Hill
Once again, the Ambrosia can be found at the top of a hill, so when heading to the point indicated on the map above, keep in mind that the resource is located on higher ground.
6 - Blocked entrance
If you go to the marker indicated on the map above, you will see a tall room, the entrance to which is blocked; you will not be able to enter from the outside. Go to the very top; you will see a heavy block there, which is obstructing the entrance to the room. However, in order to move it, you need to have the upgraded version of the Heracles' Strength power, which allows you to lift heavier objects. After you pick up the block, go through the hole and jump down into the room.
7 - The hand of a giant
It will be easiest to start at the location to which you can fast travel, that is, the statue of the God of War. From there, fly to the point indicated on the map above. The Ambrosia can be found on the hand of a statue of a giant.
8 - A rocky ledge
Simply go to the indicated point on the map above and jump down a little lower, the Ambrosia is located on a rocky ledge.
9 - Garrison
There is a small hill near a garrison, which is surrounded by a wall, you will find the Ambrosia atop the aforementioned hill.
10 - Small island
The Ambrosia is located on a small island; your wings will be the best and the simplest alternative for reaching the remote isle. It is also worth investing in stamina potions beforehand.
11 - Top of a tall structure
You will find the Ambrosia at the very top of a structure, on the right side. It is located very high up, so it is a good idea to stock up on stamina potions in advance. Be careful, as there is also a group of enemies at the very bottom of the building.
12 - Ruined fort
You will find the Ambrosia near a ruined fort, there is a statue of a giant very close to the structure.
13 - Underwater puzzle
Go to the point indicated on the map above, then jump down towards the sea. There is a puzzle to solve there. Put the surrounding stones on the pressure plates with feather symbols. Then dive into the water and swim inside the nearby tunnel. After that, you will have to climb all the way up a wall in order to reach the Ambrosia. It is worth investing in stamina potions to complete the climb.
14 - Wall
The Ambrosia is located near a wall, on a small hill. Go to the point indicated on the map above, place your character at the height of the wall and jump a little lower to reach the Ambrosia.
15 - Underwater cave
Go to the point indicated on the map above. The Ambrosia is located on a small island, away from the mainland areas of the region. In order to reach the resource, you have to glide to the island, and then travel to its other end. After that, you have to jump into the water; you will see a characteristic glow in it. The aforementioned glow marks the perfect spot for you to dive into the water and then swim straight into a cave. The Ambrosia can be found inside.