What Does This Button Do?

My guildmates and I finally achieved this after several failed attempts. There's valuable information here but for some reason I just couldn't understand. Here is exactly how we did it:

Before I explain, if you look around the room, there are 4 lion-like statue heads mounted on the wall. They shoot out daggers during the boss fight. The red gems spawn in the mouth. You only have to keep an eye on the NORTHWEST mouth and the SOUTHEAST mouth (refer to minimap). It's best to assign two people, one for each location when it's ready to click.

1. Start fight > DPS boss like normal.

2. At 66% health, a red gem will spawn on either the NW or SE location (for us, it spawned at the SE location first. I didn't pay attention if it always spawned here first or not, but that doesn't matter since you will always have the same two locations spawn gems in the end). LEAVE IT ALONE.

3. Continue DPSing boss until 33%, second red gem will spawn in the opposite corner of the first red gem. You should now have two red gems, one at the SE mouth and one at the NW mouth.

4. Clickers went to their assigned spots and coordinated clicking it them at the same time. I believe you only have a few seconds to click the second gem once the first one is clicked so make sure they time it well. One of our failures was because one of our members kept getting knocked away by the whirling axes that were near the mouth so he couldn't click it in time.

5. If you did this correctly, a red beam should be shooting out from both mouths at the same time, and the achievement will come soon after.

TLDR: DPS boss until 33% (second gem should spawn now) > click NW and SE gems at the same time > Congrats on your achievement!

Please let me know if you need any clarification, I want to make sure this is clear as possible. Good luck achievement hunting!

"Darn you Dee Dee."

Quoted from the achievement guide:

"This is one of the hardest achievements so far so I will go into a bit of detail for how to complete it.
During your encounter with Xin he will activate several traps in the room. Starting with Axes as you engage him, Blades as he reaches 66% health, and Crossbows at 33%.
When these crossbow traps activate two crystals will spawn along with them in their mouths, roughly 30 seconds appart. One in the Front Left of the room, and one at the Back Right of the room.
You'll know when this happens as you will see the emote of 'You hear a faint clicking noise...'
When a crystal is clicked on by a player they will each fire a red beam at the crossbow trap in the Back Left of the room, lighting up one of it's eyes.
If you click both crystals in opposite corners of the room together, it lights up both eyes of the crossbow trap and allows you to use a newly formed crystal, to fire it at Xin.
For our successful attempt we placed the healer in the middle of the room (as the crystal clickers are standing in the mouths of active crossbow traps) and placed the tank in front of the activating weapon trap in the Back Left."