Chart D is for the plot devices, maguffins, or odd bits of alien technology that show up. Chart E is the plot twist about the larger campaign that the plot reveals. I have used a mix of actual elements of planetary romances I have read and some ideas that sounded good to me at the time. However, some word on the general plotting of Edgar Rice Burrough Barsoom-style tales is worth some time.
To be loose, general, and a little facetious, the general Edgar Rice Burrough style plot should resemble:
Villain(s) enact an Evil Scheme (usually involving the kidnapping of Dejah Thoris or another princess) that leads our hero to pursuing the Villains across the planet resulting in the Revelation of a Secret that affects the setting. In the end, the hero triumphs (usually rescuing the princess and killing a lot of bad guys along the way) with a different understanding of the world.
On with the charts.
Chart A: The Villain(s)
d10 Result 1 Cowardly and Treacherous Noble 2 Wise Scion of a Dead/Dying Race 3 Cold and Amoral Alien Scientist 4 Heartless Assassin 5 Rival 6 Bounty Hunter 7 Slavers 8 Pirates 9 Bandits 10 Cultists
Chart B: Evil Scheme
d Result 1 Kidnapping 2 Theft 3 Exploration 4 Chase 5 Attack 6 Brainwashing 7 Brain-stealing 8 Dishonor/Besmirch 9 Sell into Slavery 10 Imprison/Transform/Make Comatose
Chart C: Victim or Ally
d10 Result 1 Beautiful Princess 2 Noble Savage 3 Brave Warrior 4 Strange Alien 5 Scientist/Philosopher/Scholar/Priest 6 Ousted Nobleman 7 Misunderstood Scoundrel 8 Loyal Handmaiden 9 Brute with a Heart of Gold 10 Warrior-Maiden Who Will Not Allow Herself to Love
Chart D: Plot Devices & Maguffins
d10 Result 1 Ancient Weapon of Vast Power 2 Terrible Monster from the Dim Past 3 Advanced Power Source 4 Terraforming Device 5 Last Scion of an Ancient Race 6 Device that Will Make the User a (Near-)God 7 Mind Control Device 8 Army of Robots 9 Library of Lost Knowledge 10 Still Functioning Computer/AI/disembodied brain(s)
Chart E: Secret That The Plot Reveals
d8 Result 1 Lost City of Ancients Who are Now Degenerate. 2 Lost City of Ancients Who Have Vast Mental Powers But are Now Amoral 3 The Truth Behind the Locals' Belief About the Gods 4 A Terrible Monster Worshipped as a God 5 A Terrible Danger That is Coming From Far Away 6 A Lost Race Who Secretly Manipulates the World 7 The Villains Are Even Worse Than They Seemed 8 A Prophecy of Great Import