how the nebula boosters work
These are not items you can hold. They pop off enemies you strike while wearing the full Nebula set, hang in the air where they appeared, and get pulled in from a generous distance. Grabbing a second while the buff is running adds a layer rather than resetting the timer, up to three deep, and the layers fall off one at a time instead of all together. Staying aggressive is what keeps the stack near the top.
why it matters for magic
Ordinary mana regeneration collapses the moment you start firing, which is exactly when you need it most. This ignores that rule entirely. It ticks at a fixed rate whether your bar is full, empty, or draining under a weapon you are holding down, and that is what lets Nebula armor sustain channelled magic without a single potion.
in multiplayer
Anyone can collect one, Nebula set or not, and picking it up hands the buff to everyone standing nearby. If you are on a team, only teammates in range receive it. One person in Nebula armor effectively feeds the whole group, which is worth building your positioning around when only one of you has the set.