Really stiff looking spiritomb! She’s a member of Johto’s Elite 4, taking place of the “dark type” user Karen (this is based of HGSS)
In her “civilian” form, her power and even the power of her keystone is in the “flower” on her hair. Without a keystone to ground her, she’s far lighter and tends to float around in place of standing. Still enough power resides from the keystone to prevent her from phasing through walls or turning invisible. In this form her attack power is nearly diminished and her speed is raised by half.
When in battle the flower unfurls to release her power, thus changing her outfit as well, which is a manifestation of her keystone and power. In this form she can no longer freely float around, and is duly grounded, however her attack power is fully utilized and her speed halved.