Season 3 began airing on September 5, 1988 and concluded after 20 episodes on September 30, 1988. The season started with the airing of the "ThunderCubs" five-parter. These five episodes revealed that Thundera had reformed, and they also offer an explanation as to why it exploded in the first place. The episodes then focus on the ThunderCats traveling to this New Thundera and encountering a number of new dangers, including Mumm-Ra.
Many of the episodes in Season 3 revolve around ThunderCats' search for the missing pieces of the Treasure of Thundera and the problems that they encounter while doing so. Also revealed are the Book of Omens and the Guardian of the Book of Omens.
The main villain in most of the episodes is Mumm-Ra with the Mutants lending a helping hand as well. The Lunataks only appear in a handful of episodes. Interestingly, the season almost feels like the final season as all of the ThunderCats' main enemies, namely Mumm-Ra, the Mutants, and the Lunataks, are either destroyed or incarcerated for good in this season's episodes.
The Lunataks are imprisoned on Exile Isle, the Mutants are captured by Captain Bragg and Mumm-Ra is seemingly destroyed by the Ancient Spirits of Evil. However, all of these villains stage a comeback in Season 4.
|3.01||ThunderCubs - Part I||September 5, 1988|
|3.02||ThunderCubs - Part II||September 6, 1988|
|3.03||ThunderCubs - Part III||September 7, 1988|
|3.04||ThunderCubs - Part IV||September 8, 1988|
|3.05||ThunderCubs - Part V||September 9, 1988|
|3.06||The Totem of Dera||September 12, 1988|
|3.07||The Chain of Loyalty||September 13, 1988|
|3.08||Crystal Canyon (episode)||September 14, 1988|
|3.09||The Telepathy Beam||September 15, 1988|
|3.10||Exile Isle||September 16, 1988|
|3.11||Key to Thundera||September 19, 1988|
|3.12||Return of the ThunderCubs||September 20, 1988|
|3.13||The Formula||September 21, 1988|
|3.14||Locket of Lies||September 22, 1988|
|3.15||Bracelet of Power (episode)||September 23, 1988|
|3.16||The Wild Workout||September 26, 1988|
|3.17||The Thunderscope||September 27, 1988|
|3.18||The Jade Dragon||September 28, 1988|
|3.19||The Circus Train||September 29, 1988|
|3.20||The Last Day||September 30, 1988|