Caveat: this year’s Inkvent appears to have elusive ink colours. I suggest reading my description of the inks and not going by the photos alone, and comparing my results with those of other reviewers.
The Diamine Inkvent calendar is an advent calendar with 24 tiny (12ml) bottles of fountain pen ink behind 24 doors, and a larger, 30ml, bottle of ink behind the 25th door. All the inks are limited edition, and, at the moment, only available through this calendar.

Day 9’s ink is Diamine Storm, a blue ink with silver shimmer.

Diamine Storm shades a little, doesn’t sheen, but does have some lovely silvery shimmer.

Here’s a Col-o-Ring swab of Diamine Storm. It’s a shade lighter in the photo than in real life.

I used a Monteverde Giant Sequoia with an omniflex nib. The nib on this pen is hard starter, regardless of the ink in it, but once it gets going it flows beautifully.

I sketched out a stormy scene from the Tel Aviv port, where I used to run regularly.

This was drawn on a Kanso Sasshi 3.5” x 5.5” Tomoe River Paper notebook (the notebooks I have were bought in 2016, and so they contain the old Tomoe River paper).
Finally, I wrote a page in my Midori Journal:

I like Diamine Storm, but not enough to justify purchasing a full bottle of it. Even with the shimmer, it’s the most pedestrian of the 2021 Inkvent inks so far. It works well with the winter theme, but I have a feeling that this will be an ink that fades into the background while other more interesting and vivid inks in the set take centre stage.