ThunderCats - Season 3 Episode 17 The Thunderscope

Back visiting their old wreckage site, Lion-O and Snarf stumble upon the Thunder-scope, a legendary thunderian telescope that locates lost thunderians, and their belongings. Mumm-Ra, interested in the Thunder-scope so he could find the treasure of thundera, ambushes Lion-O. He actually kills him in this scene. Before Lion-O dies, he manages to take out a lens from the Thunder-scope so Mumm-Ra could not completely use it. Jaga appears to Snarf, and Lion-O's dead body, and revives him. Mumm-Ra comes back for the missing piece, and Lion-O has to stop him.