...where is it?

in yaga shura's fortress, one heart is in the brazier, and the other one is in a circular "chest" between the captive warrior woman and imix

Actually, you forgot to mention that you have to open doors to the sides of where you get Yaga Shura's heart...I missed those doors the first time cuz they are so damn big...and I was busy fighting fire giants and looking for traps....