Blood in a dream commonly represents life force and vitality, so its appearance often signals that something important is at stake or feels like it's being drained from you. Seeing blood without injury can point to unresolved pain finally surfacing, something you've carried quietly that now needs acknowledgment.
The forms of the complex world obey the astral forms and that's why theurgists determined them according to the stars, in relation to whatever they wanted to influx. - Ptolomeus