In the end of Episode 6: Jabba's Palace, you have to beat the Rancor. First, activate the panel on the right or left side. This will cause a Gamorrean Guard to drop out from the enemy producing tubes.

Let the Rancor grab the enemy and it will walk to a corner to eat. Pull the switch next to the rancor and an explosive box (shoot it to blow it) will drop down. This explosive is the only way to damage the rancor.

Drop in another Gamorrean Guard to repeat the process. This time, the rancor will walk to a different corner but a similar switch for the explosive box will be present.

Repeat the Gamorrean Guard drop for a third time and the rancor will walk to the door where it came out from. Use the non-droid characters to pull both switches by the door to defeat the rancor once and for all.