Warm Stone

The Warm Stone is a magical stone that retains intense heat or cold over long periods of time, allowing it to freeze distant liquid or melt distant ice. It lets the player access mandatory and optional locations they couldn't otherwise.
== Warm Stone Forms ==
The Warm Stone is initially received as the Warm Stone, but it has no power in this state. It must be heated or cooled to change form and have effect. After it is used to get past an obstacle, it reverts to the Warm Stone form.
When the Warm Stone (or Cool Stone) is heated, it becomes the Hot Stone, allowing it to melt ice into liquid water. Heat the Warm Stone at the hot spring in Whisker Woods. Other hot liquids, like the Inferno Cave magma pools or the Polar Fields hot springs, won't work. 
When the Warm Stone (or Hot Stone) is cooled, it becomes the Cool Stone, allowing it to freeze water and magma. Cool the Warm Stone at the ice pond in Polar Fields, adjacent to the pond fishing pier.
== Warm Stone Uses ==
The first use of the Warm Stone, and the only mandatory use, is melting the waterfall in Whisker Woods after Ivlet freezes it. Here, Arvin first gives the player the Warm Stone, helping them restart Godfrey's water wheel by resuming the flow of water with the Hot Stone.
For Charles's optional quest, the player must bring the Hot Stone to Polar Fields, melting the ice block by the pond fishing pier to access the sea pier. This sea pier is the only place they can catch the Golden Angler Fish (Catz) or New Breed Rainbow Fish (Dogz) to complete the quest, and it also hosts many other valuable and exclusive fish.
There are two optional uses for the Cool Stone. The player can freeze a pool of magma in Inferno Cave to cross it. Then, they can find a Top Quality Canned Fish (Catz) or Meat (Dogz) and, potentially, the rare Lychee. They can also freeze the eastern river in Crystal Caverns to cross it. There, they can find another Top Quality healing item and, potentially, a Potato.
Aside from the mandatory waterfall quest, any terrain changed by the Warm Stone will revert to its normal state when the player leaves the area. Therefore, doing fewer, longer fishing trips in Polar Fields can minimize backtracking to Whisker Woods for the Hot Stone, as opposed to taking more, shorter trips. If they're angling for a specific Polar Fields fishing setup, they should save at the Polar Fields Warp Stone before using the Hot Stone to melt the ice wall. That way, they can reset the game without saving if they do not get their desired setup, allowing them to refresh the setup without needing to reheat the stone.