This design is based off a jellyfish, since if a jellyfish is found in a nightmare, it means you have past regrets. And its shoulder pads look like the "Man O' War" jellyfish. I chose jellyfish for the design because it has the same flowy feel Darkrai has.
This pokemon can be found lurking in the depths of the ocean, wandering. Although this pokemon has potent venom, that can send you into a forever nightmare causing your body to convulse, it rarely ever attacks humans. However, if you happen upon this creature, do not startle it, or else it will attack. Anyone who earns this pokemon's trust, will be forever loyal to them, letting them come carefully close.