Misty Escape

When it drops to 0 hit points outside its resting place, the creature transforms into a cloud of mist (as in the Shapechanger trait) instead of falling unconscious, provided that it isn't in sunlight or running water. If it can't transform, it is destroyed. While it has 0 hit points in mist form, it can’t revert to its creature form, and it must reach its resting place within 2 hours or be destroyed. Once in its resting place, it reverts to its creature form. It is then paralysed until it regains at least 1 hit point. After spending 1 hour in its resting place with 0 hit points, it regains 1 hit point. (Vampire, pp. 297, MM)