  High energy ${\gamma}$-rays are powerful probes in the search for
annihilations of dark matter (DM) par- ticles in dense environments. In several
DM particle models their annihilation produces characteristic features such as
lines, bumps or cut-offs in their energy spectrum. The High Energy Stereoscopic
System (H.E.S.S.) of imaging atmospheric Cherenkov telescopes is perfectly
suited to search for such features from multi-TeV mass DM particles. The Dwarf
Spheroidal Galaxies (dSphs) of the Local Group are the most common satellites
of the Milky Way and assumed to be gravitationally bound dominantly by DM, with
up to O(10 3 ) times more mass in DM than in visible matter. Over the past
decade, several observational campaigns on dwarf satellite galaxies were
launched by H.E.S.S. amounting to more than 140 hours of exposure in total. The
observations are reviewed here. In the absence of clear signals, the expected
spectral and spatial morphologies of signal and background are used to derive
constraints on the DM particle annihilation cross- section for particle models
producing line-like signals. The combination of the data of all the dwarf
galaxies allows a significant improvement in the HESS sensitivity.
