ThunderCats S01 E21

ThunderCats S01 E21 "Birth of the Blades"
After defeating Ratar-O, the ThunderCats do not have enough time to hide the Sword of Plun-Darr, as Mumm-Ra and his Lizard Army have already arrived. Pumyra suggests that they use the Sword of Plun-Darr to help lure away the Lizard Army through the mines while giving time for the refugee cats to escape. Lion-O decides to split the team: himself and Pumyra distracting the Lizard Army, while the remaining ThunderCats stand by at the Thundertank. As Lion-O and Pumrya run through the mines, Mumm-Ra uses his connection to the Sword of Plun-Darr to act as a tracking beacon. Every time the two think they are ahead, Mumm-Ra's forces manage to corner them, and they are forced to flee. A flashback reveals the origins of both the Sword of Plun-Darr and Sword of Omens. Mumm-Ra was directed by the Ancient Spirits to collapse the star of Plun-Darr in order to harvest its ore to produce a weapon to channel the Powerstones' energy. After successfully destroying the star at a cost of billions, the entire star system was reduced to a small collection of ore, which Mumm-Ra collected to forge the Sword of Plun-Darr. Disillusioned by Mumm-Ra's methods to achieve peace, Leo secretly recovered the discarded shards of the ore to secretly forge the Sword of Omens. In the present, Lion-O and Pumrya split up in an attempt to distract their enemies. However, Mumm-Ra captures Pumyra and regains his sword. Lion-O and Mumm-Ra fight and Lion-O gains the upper-hand, but he choeses to save Pumrya's life over preventing Mumm-Ra from retrieving the Sword of Plun-Darr. When sunlight starts pouring into the holes in the mine made during the battle, Mumm-Ra retreats. Although the Sword of Plun-Darr is lost to Mumm-Ra, Lion-O gains Pumrya's respect. However, the gravity of their situation has increased.