Thundora is an Evolved form Spectrobe of the Corona Property. It is the Evolved form of the Child form Spectrobe Thunba, and evolves from the Adult Thundor. The Evolved form Spectrobe Windora is it's "sister" Spectrobe.
In the original Spectrobes, Thundora can only be obtained through Nintendo Wi-Fi Connection, the only Spectrobe in the entire series that can be obtained through this method. Spectrobes: Beyond the Portals gives it its Child and Adult forms.