Here is a simple guide on how to find the Abyss Watchers Boss.
Level 3, Siberiade
To find the Dark Souls Easter Egg boss go to the end of the third level.
Under the bridge just before the level ends you will find a secret passage.
The Boss Strategy
You will meet 3 Knights (4 on Serious Difficulty) with a very familiar move set to those who have played Dark Souls 3.
They are able to block damage with their shield and become invincible while rolling a very difficult fight to shoot your way through…
I found it much easier to fish for back stabs using the Brigand Twin Daggers and utilize your mobility to evade their attacks
