HESS found several new TeV sources in the Galactic Plane Survey. Possible origin would be PWN or synchrotron X-ray SNR shell. However many of these new TeV sources (their sizes are ~10 arcmin) have no counterpart in any other wavelength. They can be main contributors to the Galactic Cosmic rays. In order to reveal the nature of these fantastic objects, we propose to observe the extended sources. HESS~J1616-508 is already observed and we found this source has quite low surface brightness in X-rays compared with TeV gamma-rays, indicating this is a dark particle accelerator Here, we point out HESS~J1804-216 which has possible counterparts in other wavelengths, then it might be the missing link between known Galactic accelerators and dark particle accelerators.