After defeating the High Preistess, you will be brought back to the city of origins proceed right where you could not b4 until you reach The City Walls. Within the city walls after a short walk through you will come to the creatures dropping bombs and about 4 soldiers 2 orange/ 2 blue. once the creature in the air drops the bomb hit it straight on as you wait to line up two of the soldiers. (color makes no difference) 2 chances . Good luck and enjoy the achievement.
Please make a note if this can be fixed b4 putting a negative ty. =)