You transform your blood into a 10-foot-radius protective dome that forms around and above you and remains stationary for the duration. The dome can be damaged, and it has a number of hit points equal to 20 + double the amount of hit points spent in the casting of this spell. Any creature within the dome cannot be targeted by creatures outside the dome, and vice versa. Spells and attacks that would pass or extend through the dome instead hit the dome and do not extend farther. As long as the dome lasts you can use your action to expend a number of hit points and add this amount to the dome’s current hit points.
Nine creatures of Medium size or smaller can fit inside the dome with you. The spell fails if its area includes a larger creature or more than nine creatures. Creatures and objects within the dome when you cast this spell can move through it freely. All other creatures and objects are barred from passing through it. The dome is semi-transparent. It can be seen through, but things seen through the walls appear distorted and blurred with the red color of the dome.