The Mother Flame was developed by the 
scientist Vegapunk and access to it was granted to 
Imu and the 
Five Elders.
It is not clear how the Mother Flame is controlled, but the 
Five Elders were given the order to navigate it to 
Lulusia Kingdom. It moves through the air, over the 
clouds. It is unknown how fast it travels, although its presence was not detected by anyone on Lulusia until it was already overtop of the island. 
Ethanbaron V. Nusjuro implied that the Mother Flame cannot be used freely yet, however it is unknown what he meant by that.
The annihilation of Lulusia was performed as a test of the Mother Flame's power, indicating it was just recently completed. It is not known whether Imu and the Five Elders concluded it to be successfully operational following Lulusia's destruction.