My darks are among my strongest cards:
36/40 Ach Punch (my highest level/strongest card across the board)
15/15 Beidou Shengjun (he's capped - need to break it to level him more)
15/20 Bicorn
I've seen the werewolf a lot but I just use him for merge fodder. The problem I have is all these unusual cards that I'm not using but don't want to get rid of: Ashura the Evil, Ziz, Chernobog, an extra Ach Punch I'm saving to break the next level cap, Greys (x2 - have a Greys lvl 20/30 that is currently my second strongest), Nandou Shengjun, and a few other lower level cards that I don't want to get rid of.