What's wrong with "Darukin"? Does someone else have that tag? You probably won't like the way I find a tag, especially since I've been so picky. I went with "
Dryn" for a long time. It's the name of a Chozo who was a key scientist in power suit technology in the
Metroid series. You only see a
bust of Dryn. Well, other people wanted this tag as well, and it turned out someone at
Anther's Ladder had the tag. Worse, he used Samus as a secondary, and I couldn't be associated with him. Before I found this out, I went with other tags, such as Ungeist and der Rabe, German words for "demon" and "the raven". Still, I wasn't satisfied. I finally went with Crystanium, some made up material from the Metroid Interactive Fanfic (MIFF). Anyway, here's what I suggest.
1. Don't base your tag around a series. Say you're not pleased with the series anymore, or you would rather not be pinned to one series in general. Do you keep your tag? Or do you find a different one? Once you have a tag, history is connected with it.
2. Don't base your tag off of a color, unless you don't mind using a different color for your character. The reason why I used Ungeist and der Rabe was because the former sounded cool, and the latter, I like ravens. Well, what if I was using Dark Samus for the palette and someone else was, too? It's a popular palette choice, so imagine I would have to compete with others who want to use that color. Furthermore, at the time, I was trying out Mario and ZSS for a secondary, and I prefer Mario's light blue and pink palette and ZSS' red outfit. That didn't work for me.
3. Make sure that you cover all your bases, unless you don't care that there's someone else out there with a tag like yours. Recall my problem with someone on Anther's Ladder going by the tag, "Dryn". Well, that bothered me a lot, and as much as I wanted to keep the tag, I switched for Crystanium. I checked Smashboards, Gmail, Twitch, Twitter, Discord, Anther's Ladder, &c. to make sure the name hadn't been taken. If it had for any one of these, I would have continued to think of a different tag.
But, perhaps none of these bother you. Well, then perhaps you could try out PSI Darkness. It's not an attack that exists in the Mother series, though I've been told it was going to be one, but it never happened. The reason is because you use Ness and Greninja, who is a dark type.