The Ultra Stone is an important item found in both Paper Mario and in Paper Mario: The Thousand-Year Door. The Ultra Stone serves the same purpose in both games: it allows the partners that Mario has to become ultra-ranked. The Ultra Stone cannot be acquired until Mario goes through the fifth chapter of each game. In Paper Mario, Mario gets the Ultra Stone automatically. But in Paper Mario: The Thousand-Year Door, Mario has to go out of his way to obtain the Ultra Stone. There is also a difference in how Mario levels up his partners. In Paper Mario, it is done by finding certain blocks in the course of the game, there being only 16 in total. In Paper Mario: The Thousand-Year Door, Mario has to give three Shine Sprites to Merlon in Rougeport.
Ultra-Rank means that Mario has the option of leveling up his partners two times instead of once. If the partner is leveled up to Ultra-Rank, they increase their health and attacking power. They increase by the same amount as they did from normal to Super-Rank. Like with Super-Rank, they learn a new ability that is more powerful but requires more FP. This system is the same for both Paper Mario games with an Ultra Stone in it.
Paper Mario
In Paper Mario, Mario gets the Ultra Stone in Jade Jungle. After reaching the end of the jungle, Mario meets Raphael the Raven. Raphael opens a mode of transportation needed for Mario to proceed to Mt. Lavalava. Raphael the Raven also automatically gives Mario the Ultra Stone after preforming this task. Since this event is needed to move onward in the game, Mario automatically gets the Ultra Stone without added effort.
Paper Mario: The Thousand-Year Door
After Mario returns from Chapter Five with Bobbery, he can find Merlon waiting outside his house. Merlon tells them that he had a vision of something involving Mario's partners. Merlon also tells them that it has something to do withHooktail Castle. If Mario goes back to Hooktail's Castle, Mario can find a crack in the wall. This wall is part of the room containing the key to the Black Chest Demon. This crack can be blown apart into an opening with Bobbery. If Bobbery destroys the crack, Mario finds a secret room with a treasure chest. This chest does not contain the Ultra Stone, it contains the Up Arrow.
If Mario returns to Merlon in Rougeport, he can give him the Up Arrow. Merlon then remembers that he bought something useful from a Flea Market, but left it up in the attic. Merlon flies upward, like the Up Arrow tells him too, and he finds the Ultra Stone. With this, Mario can now choose to upgrade his partners to Ultra-Rank if he has enough Shine Sprites.