Put That Thing Back Where It Came From

To earn this achievement, you must complete Dawn of the Infinite on Mythic difficulty after collecting four Time-Lost Artifacts throughout the dungeon and then 'restoring' them during the last boss fight.
After activating the RP at the beginning of the dungeon, you will receive a buff, which is required for the artifacts to spawn. If ANYONE in your group dies, everyone will lose the buff and you will have to reset.

The Time-Lost Artifacts resembles small hourglasses and spawn after defeating certain bosses throughout the dungeon:

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• The first one is found after defeating [npc=206238] and spawns behind the middle portal on the left-hand side.
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• Second artifact is found after defeating [npc=198998] and spawns on the boss platform opposite the ramp going towards the temple.
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• The last two are found after defeating [npc=202789] and [npc=209208] and spawns in the middle of their respective boss platform. It doesn't matter which boss you kill first.
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The artifacts need to be picked up by 4 different players and taken to the last boss of the dungeon, [npc=199000], without dying. When picking one up, you will gain a debuff, which prevents mounting and Evoker/DH's from double jumping. Even though this doesn't sound much of a challenge, you have to be careful when traversing the bridges with the sand orbs later in the dungeon. You don't want to fail a run to someone getting knocked off, so make sure not to trigger the orbs OR simply let the players with the artifacts run first. :)
It doesn't seem like you can backtrack after defeating [npc=194907]/entering the Infinite timeline, so make sure to pick up the first artifact before doing so!

Artifacts can be dropped and picked up again if needed, but when it is dropped a 'bomb' timer will start and if it runs out ALL looted artifacts will DESPAWN.
DRUIDS BEWARE: Shapeshifting into Mount Form will automatically DROP the artifact on the ground and start the timer as if you had done it manually. I learned this the hard way after getting the brilliant idea of carrying our wheelchair Warlock without noticing that I dropped the artifact behind me....

To complete the objective on the last boss, you will have to bring ONE artifact to each of the 4 [npc=205212] adds that spawns during the fight. Simply go inside the grey ring indicator around the add (only visible while holding an artifact), which will automatically throw the artifact into the add portal (no need to use the action button). Note that the 2 last adds will spawn at the same time, so be ready!
After you have thrown one artifact into each portal, kill the boss as normal (still without anyone dying) and you will earn the achievement and your [item=208490] transmog for ALL armor types!

Disclaimer: I do not know if you can die after completing the artifact objective on the last boss, but I assume that you will need to have the [spell=418806] buff to gain credit.
Edit: Spelling, updated objective explanation and disclaimer.

, or so help me!

Sadly can't be soloed. Bosses are easy, but i can't split myself into 4 people :/