Hey! Now that I finally have an Orb of Aether during a Tomb event, I’d like to show off one of the many ways to take advantage of the item. In public tombs one of the first things that you want to do is paralyze all three of the bosses on top of each other so that they are easier to permastun and easier to pierce. The Orb of Aether is very good for paralyzing any group of enemies on top of each other. However, unlike in my previous guide for farming Greater Nature Sprites, the enemies you want to paralyze do not spawn at one center point. Rather, they circle in the same direction, and you have to use careful placement to stack all three bosses. The first concept to understand is that all three tomb bosses circle in a counter-clockwise direction, but if a tomb boss is paralyzed, it will begin circling in the opposite direction (clockwise) once the duration of the paralysis ends. The second concept is exactly how the Orb of Aether works. The part that matters in this guide is the paralysis. It pulses every second, delivering a paralysis over an AoE (radius 2.5 tiles) which lasts until the next pulse. Meaning that as long as the orb is placed down, an enemy will remain paralyzed. The problem is when the orb disappears and a new one is placed. If there is only one mystic with the Orb, they can still place one down as soon as the first disappears, as the duration is exactly the same length as the cooldown. 5 seconds. However, the Orb takes about one second to activate after it is placed down, which is long enough for the enemies paralyzed by the previous trap to start moving again if you do not time it perfectly (which is quite hard to do). When we look at both of those concepts, it becomes clear that placing the orb at the exact location you want them to stack does not work. Say you place the orb on Bes. When Geb comes around, it will be paralyzed approximately 2.5 tiles away from Bes (2.5 is the radius of the paralyze effect). When you replace the orb at the end of the cooldown, if not timed perfectly Geb will become temporarily unparalyzed and begin to circle clockwise (away from your orb). Even if timed perfectly, Geb will remain 2.5 tiles away from Bes for the duration of the fight, as will Nut. This is preventable by placing the orb in front of Bes. To be exact, 2.5 tiles away. Since the orb of Aether is placed in the center of the tile closest to your cursor, you can measure exactly which tile you should place it before the bosses activate. In the below image, you will see that your orb will hit Bes’s hitbox (black) when the orb is placed either two tiles down and one right (red), or one tile down and two right (blue):
To reiterate, the reason the orb is placed to the right and down is because it places it in the path of Bes as it rotates counterclockwise when it is first activated. It leaves a bit of room for error because it allows the bosses to rotate toward your orb in case they come into range between pulses:
As seen above, Bes moved about one tile after being activated, but was still caught inside the orb’s range. I personally prefer to place my orb at the blue x because Nut has a tendency to circle the room at a shorter radius than Bes, causing her hitbox to occasionally pass the radius of the Aether Orb in between its pulses and therefore avoid being paralyzed. In the above image, Geb was not stacked on top of the two because there was a pesky archer nearby who accidentally paralyzed it before it rotated to group.
Once the three bosses are stacked at approximately the same location, you can start placing your Orb of Aether in the middle of all three to allow for error (in that one second where the orb is being armed) and also to paralyze all the artifacts.
Set:
I highly recommend using the Esben staff, as it is the only staff able to pierce while shooting forward. It’s shot pattern is actually quite helpful, as it aids you in hitting all three bosses even if they are not perfectly stacked. You can play around with your distance from the targets and where you aim it in order to hit all three.
Any robe and ring is adequate if you have a max rare pet as it supplies sufficient mp heal for you to keep all three bosses paralyzed for the duration of the boss fight. If you do not have a good enough pet, you may want a robe/ring that boosts mp. Any bit helps-- depending on your pet you should be able to regenerate at least most of the 90 mp spent on your ability by the time the cooldown ends.
Anyway, happy grinding! May there be many loots and lutes in your future 
(sorry I had to)