This achievement can easily be unlocked very early in the game.
You can unlock this achievement as early as in the beginning of the story mission “Rude Awakening
” in Fornburg, Norway at the beginning of the game. This is where I unlocked it.
Rude Awakening is the first opportunity you are able to assassinate an enemy from your horse as assassinating enemies is introduced to you in the story mission "The Prodigal Prince" which is directly before it.
- Call your horse by holding
on the directional pad.
- Mount your horse by pressing
- Press to crouch on your horse.
- Silently approach an unsuspecting enemy and the “Assassinate” prompt will show up.
to assassinate from your horse.
The achievement should unlock immediately after.
* There are some practice dummies in Fornburg, Norway (close to the docks) that you can use to assassinate from your horse.
* There are some practice dummies around the Hidden Ones Bureau (after you build it) in your settlement in Ravensthrope, England that you can use to assassinate from your horse.This is a video of how it is done: