Do Echoids Dream of Electric Sheep?

You found Cosmos, Encore's wooly companion, by a mysterious gateway. Some kind of test seems to be running behind the gate and it needs your assistance.
During the test, Cosmos will provide Echoids to significantly boost Resonators' combat power.
You can complete the task with your friends.

Available after reaching Union Lv. 22 and unlocking Co-op Mode

[About]
Cosmos has shown up near a strange gate, asking you to go inside and assist with some kind of test.
The worlds behind the gate intertwine in a tapestry of mystery—
"Kind Rover, may you find your fortune in the lucid world."

[Eligibility]
Reach Union Level 22.

[Event Rules]
1. Defend the experimental device and defeat the Tacet Discord to achieve the ultimate victory!
2. Cosmos will provide special Echoids to help the Resonators.
2. You can only use designated Echoids in this mode (Sonatas will remain effective and only the main Echo Skill will be replaced).
3. Points = (Remaining time per wave x time coefficient) + (Remaining device HP at the end x level difficulty coefficient)
4. The cap on total points will increase with higher levels unlocked. Replaying stages allows you to accumulate more points.