Psyrens (OC Grimm idea)

These mermaid-like Grimm are very elusive as they are vicious like other Grimm. Combined with their speed while swimming, they use their angler fish-like lures to attract their prey by making them see what they desire most, be it treasure or loved ones, anything. If the prey is behind some glass, they see the Psyrens for what they are when they start glitching between forms.