Originally Posted by twilightdream

I really have no idea who I may pick.
For now I'm looking for pierce 6* unit and only Mistletoe and Mei Plumblossom not in my team.
Mistletoe is out of question I not build any counter team. So Mei Plumblossom? No... way...

You can always pick Mistletoe and prepare to make a counter team sometime later? They're really devastating, and counter girls are the ones making most use of event equipment, since DEF is also an offensive stat to them.
While Mei is one of the three knights I usually look for when borrowing a helper squad (at least, when speed isn't an issue), because I use solar blast, and starting with an extra 50% fill on the bar is nice to get an early blast.