Jaxi Skip
Jaxi Skip, also known as Jaxi Ruins Skip, is a speedrun trick that allows Mario to quickly reach the top of Jaxi Ruins in the Sand Kingdom using a Bullet Bill from the main area of the Tostarena Ruins, circumventing the Ice Cave.
Execution
The trick begins by capturing a Bullet Bill from the Tostarena Ruins and flying over toward Jaxi Ruins. In most speedrun categories that use this skip, players will collect the On the Leaning Pillar moon as the Bullet Bill on the way over to Jaxi Ruins.
The Bullet Bill should be crashed into a specific spot toward the right side of the western wall of the structure (pictured at right). This spot can be identified as the upper left corner of the face emblem on the corner of the structure. After the Bullet Bill explodes and Mario is forced out, wall jump against the wall. At the peak of the wall jump, cap throw and dive onto the top of Jaxi Ruins.
Alternate methods
There is another way to skip the underground area that does not involve the use of a Bullet Bill. It involves traveling around to the other side of the ruins where the two Jaxi statues are located and using them to reach a thin ledge partway up the structure, which can in turn be used to reach the top.
Speedrun usage
Any% & Dark Side
This trick is present in all Any% routes for the Sand Kingdom, as well as in the Dark Side run. It also allows the player to collect 50 coins from the chest atop the ruins without taking any additional time, if they open it while waiting for the Power Moon to become solid. This is useful since the Any% run relies on the purchase of two shop moons. Optimally, the captureless variant is used in Any%. This slight reroute is known as "Reverse Jaxi" and involves collecting the Jaxi Ruins moon before On the Leaning Pillar and Inside a Block is a Hard Place. This route can be paired with Invincibill in Any%.
World Peace
In World Peace, this trick is present in the beginner route for Sand Kingdom. Activating the checkpoint on the platform allows the player to return to Jaxi Ruins later after defeating Hariet, placing them near the entrance to the Underground Temple.
The advanced route does not utilize this trick, in favor of using Dram Strat as an element in the route to collect additional moons.
Darker Side
In Darker Side, the captureless variant of this trick is utilized just after collecting On the Eastern Pillar.