Like Sands Through the Hourglass

Changed in 10.0.7 to only need 20 orbs caught instead of every orb.

If you are tracking the achievement, it will stay red even after you have caught 20+, so just count them out then kill boss when you have enough, probably should catch extra just to be safe.

Easy Solo (preferably pet classes) for Level 80-100 Worldsoul Saga & Beyond...

0. Achievement Tracker enabled will change from Red to White upon satisfaction of criteria.

1. Mythic Difficulty.

2. Begin fight.

3. Pet tank boss in middle of room, you get to stand closer to edge of room, if no pet you get to drag boss around with you, lol!

4. Eternity swirls form under your feet, and you can see them dropping down. Stay in swirl until you catch one, then move to the next.

5. Tracker will turn from red to white once you have all 20.

6. Kill boss.

7. ?

8. Profit. Achievement Completed.

After over 8 hours wiping and attempting this achievement SOLO. I found a way to do it as a Blood DK.

Jumping and standing on the RIGHT Brazier (If you look at the room from the ENTRANCE of it). Using AMS as soon after the boss casts the first Eternity Orb, and then Death's Advance as Wing Buffet is about to be casted. Then once the boss' energy has gone down to zero, he starts Phase 2 which I focused on burning him down as much as I could as it increases your haste by 50%, while recovering some of my health, making sure I'm above 90%. Once Phase 1 repeats, this time I've used AMS + Death's Advance as soon as Wing Buffet is mid-cast. The reason for that is that the first time you encounter him, he casts Time Sink immediately as he uses Eternity Orb, and on the SECOND Phase 1 he casts it AFTER Wing Buffet, not before. Luckily I've also recorded it, and the only person I had with me was a Mage who simply stood with me just for about ten seconds before dying from Wing Buffet.

If you want to do this for your party, solo, do this in summary:

Run back to the right brazier, jump onto it. Your party can either be outside, or remove ALL of their armor and stand with you on the brazier, then die from Wing Buffet, if they don't die fast enough, an orb will spawn away from brazier, causing the achievement to fail.

Once you are positioned, engage with the boss. As soon as he casts the first Eternity Orb, use Anti-Magic Shell. Good job, you've prevented the first Time Sink. Once that's over, Be ready to use Death's Advance after the first Sand Breath as Wing Buffet is about to be casted which will knock you off the brazier if you DO NOT have movement / knockback immunity also known as Death's Advance.
Once Wing Buffet is over, you are practically done and no longer need to worry about anything that knocks you off, you can focus on healing yourself anda burning the boss down.
Phase 2 beings:
Use everything that you can to burn him as much as you can during that phase, make use of that massive buff, however keep yourself healthy, at least above 80% if not 90%.

Phase 1 repeats itself, but with slight changes;
The first change is with Time Sink. Time Sink will be casted two to four seconds AFTER Wing Buffet. You must always use both AMS & Death's Advance as soon as you see Wing Buffet being casted and once you do that, you will be preventing both Time Sink and getting knocked off the brazier from Wing Buffet. Once that is over, you're practically done. Everything repeats itself, with no changes. You just have to focus on survival more than anything.

The talents I've used:
https://www.wowhead.com/talent-calc/death-knight/blood/DAPRVRUBSEVBAFFJoUANVVJIUVREVUYFBBQ

Or an import link for in-game: BoPAdLUHklrTr3hBIcYWdbnCGDCJJCJJiISERiIhgkkEJAAAAAAJSiDQk0kISAAAikkkAAAAA

A link to the full video: https://www.youtube.com/watch?v=ZgUtYSj0l04