Monstones are sentient Stones and antagonists in Mashin Sentai Kiramager.
They are virtually mindless and seek only to find an entity to merge with to absorb its power.
In the past, a Monstone was unearthed by King Oradin while traveling with Mr. Hakaminami and his son, Takamichi. The Monstone merged with Takamichi, threatening his life, but Oradin brought Takamich to Crystalia and saved Takamichi by implanting a Kiramai Stone in his body, countering the Monstone and making Takamichi part Crystalian.
Later on, a Monstone was unearthed by Takamichi while venturing on Earth for treasure. The Monstone sensed Meteorite Jamen of the Yodonheim nearby and merged with him, granting him the power to create melting heat.
The Monstone within Takamichi was later corrupted by Galza into a Jaaku Monstone, causing Takamichi to turn evil and fall under Galza's control. The Jaaku Monstone was eventually expunged from Takamichi's body and grew giant, only to be defeated by the Kiramagers in their Mashins.
Another Monstone was later unearthed by Takamichi while searching for the Kanaema Stones, after he found the third stone Energia. The Monstone attacked Takamichi and merged with Energia, causing it to grow giant.