Unsouled

Getting to Lad’s special arena is a little bit more complicated than the others; there’s two things you’ll need to do to reach it. The first is to have Lad take out a specific pillar, it is the first one to the upper-right of the statue. From here, fight him normally until he activates his Active Soul. Now you will need to fight Lad while staying in the vicinity of the pillar’s remains, identified by the symbol seen in this achievement’s icon. Eventually, he will use an attack that will see him fly up and crash down. If he hits the symbol - and by extension, you - you will enter a pusedo-cutscene where you will clash briefly while falling before hitting the ground in the special arena, filled with water. Defeat Lad here on Master Soul for the achievement. (Like the other special arenas, after the fight, you’ll able to interact with a Gradiva statue for a passive soul that is required for Soul Taker.)

Video demonstration (note: you may have to press the third icon on the right from top to bottom, which sends you to a new URL with just the clip, to get it to play):