One of the harder things you can do in a game is hit a moving target. In Horizon Forbidden West, this is something you will need to get good at. Your aiming skills will especially be put to the test when trying to open the door at the beginning of the Death's Door quest.
How to knock off a Leapslasher Spark Coil in the Main Quest "Death's Door"?
You will need to use your scanner to identify the Spark Coil on the Leapslasher and then hit it just right with your bow to knock it off. This will likely take a few tries, but the easiest way to go about it is by sneaking up on one and hitting it from behind.
When you trigger the Leapslasher to attack you, it becomes far more difficult to get the Spark Coil. When you successfully hit the Spark Coil and knock it off, Aloy will make a comment about it. From there, you just need to pick it up and take it back to the nearby crafting table.
If you are playing the game on the easy or story difficulty, then you simply need to kill a Leapslasher to get the Spark Coil. Once it's dead, loot its body, and the item will be added to your inventory.
For more Horizon: Forbidden West guides, check out Who is Varl in Horizon Forbidden West?on Pro Game Guides.