What support does Prismana Turbo provide?

The word to focus on is Dark. This is not a general damage buff that helps whatever you happen to have on the field. It pays off when the damage your team is actually dealing is Dark, so a Prismana Turbo slotted next to a Dark carry is doing real work, and the same Turbo next to a team dealing some other element is doing much less. Build around it or leave it on the bench.

It is also an exclusive skill, meaning it comes with the Prismana form rather than with Turbo as a species. A Turbo you caught in the normal way is not quietly carrying a weaker version of this. The support is a reason to want the Prismana specifically.

If you are hunting one, note that Prismana form and shiny or sparkling status can land on the same Aniimo at once. The two rolls are not exclusive of each other, so a Prismana Turbo that is also shiny is possible rather than a contradiction.

How it differs from Prismana Glacie's support

Glacie is the useful comparison, because its exclusive skill Flickering Shot grants an unconditional 15% team damage buff for 15 seconds. Unconditional is the key word there. It does not care what your team is built around.

Turbo's support asks something of your roster in return. That is the trade between the two: Glacie slots into anything, Turbo wants a Dark team and rewards you for having built one.

Not settled: The size and duration of Turbo's Dark damage support are not pinned down the way Glacie's 15% for 15 seconds is, so how much a Dark team actually gains from it is still open.