Nightmaher (Dog's Tooth Violet)'s Blooming Gacha / ナイトメア(カタクリ)開花記念ガチャ is a promo gacha worth 2,000 DMM points. You can roll it infinitely. Nightmaher is the only 6* in this gacha. The rates differ from the usual premium gachas.
6*: 0.8%
5*: 10.2%
4*: 89%
3*: 0%

Although 3*s don't come out, Nightmaher isn't guaranteed to come out either. It's just like the Skin Gacha from before.

(The thread title differs from the gacha name because I'm avoid parenthesis in thread titles. It really screws up URLs.)