Without spoiling it, where can I find any of the embers? I've gone to Fallen Giants, Bastille, Harvest Valley, Earthen Peak, Lost Ruins, Sinners' Rise, Heide's Tower, Grave of Saints, Huntsman's Copse, Undead Purgatory.

There is only one ember in the game, and its past Earthen Peak.

The Ember can be found in the area that follows Earthen Peak.

at the start of Iron Keep...it is fairly well hidden though, you will have to look for it actively to find it

hint: it implies to jump a few times

Iron Keep.

You find it in a totally random location. It's just sitting on the ground. Good luck.