Question

What is umbrakenesis?​

Answer 1

Did you mean umbrakinesis? If so, umbrakinesis is the ability to manipulate light and shadow.

Answer 2

Umbrakinesis is the ability to manipulate light and shadow. Phoebe describes her ability as "[stealing] light" and "[channeling] darkness". The ability appears to have the capability to nullify nearby evos' abilities and disrupt electrical appliances in the user's immediate surroundings.

Hope I helped ^_^