EGG, Essential Guise Generator

It's an egg that your powered self hatches out of. Isn't that nice? I'd say I made it myself, but I got a lot of help.

- Megrez explaining the EGGs

An EGG (Essential Guise Generator) is the prized artifact of all Ovamancers. It is specifically attuned to them and activates their powered forms and abilities. As one might think, it is shaped like a fancy magical egg. It can come in lots of designs, but the one consistent element is at least one glass "window" where a colored energy can be seen.

Form and Function

An EGG's default size is about the size of a quarter. Upon pushing the button on it that primes it, it sizes up to comfortably fit in the user's palm. The button generally turns into a switch that can be flipped, opening the EGG and unleashing its power. This is how the Ovamancer's transformation sequence begins; while the Ovamancer is powered up, the EGG shrinks back down and hides as a bauble somewhere on their costume. Ovamancers power down by either pressing the button on the EGG or simply concentrating on returning the power to the device.

Emotional Attunement

An EGG works by containing and processing spiritual and emotional energy. Since it contains the energy of the person it's assigned to, aspects of the Ovamancer's personality and desires may manifest when it's activated, such as making the powered uniform in a specific aesthetic style or affecting the nature of the Ovamancer's powers.

Breaking the EGG

EGGs are not foolproof and can malfunction. They can accumulate negative energy if the Ovamancer is stressed or experiencing turbulent emotions. If too much negative energy accumulates, it can cause corruptions or malfunctions when the Ovamancer powers up, to the point that the user may become overwhelmed by their emotions and lose control. In extreme cases, a dangerous spiritual manifestation may break free of the EGG and wreak havoc, leaving the Ovamancer unconscious until the manifestation is defeated.
Staying in powered form for an extended period of time (maybe around a month) can exhaust the EGGs's energy supply and render it unable to sustain a powered form.
If an EGG is physically damaged or otherwise drained of energy, it can cease functioning. It can be fixed and replaced by Erlu the Attuner, but you'll get an earful about it.

"Putting Humpty Dumpty Back Together"

While negative consequences to using an EGG as an Ovamancer do exist, they are rarely permanent. Mindscaping (the act of entering a person's spiritual world and interacting with it) and contact with attuner gems can ease the flow of negative energy and provide a small sense of comfort to an Ovamancer. However, as Erlu says, there is no substitute for self-care, and all Ovamancers are encouraged to take care of themselves and work towards being well-adjusted in their lives. Going on hiatus till life stabilizes carries no stigma (and if anyone gives you trouble, they'll get an earful from Erlu).
Becoming an Ovamancer is intended as a celebration of the possibilities of existence. Suffering while powered up to the point of malfunction defeats the purpose.