Three Rulers of Mt. Rappaslea

Three Rulers of Mt. Rappaslea refers to a group of monsters that rule over Mt. Rappaslea.

Background
These monsters are the rulers of one of the mountains in the Azerlisia Mountains. The sky is ruled by the Phoenix Lord, whereas the Ancient Flame Dragon ruled the earth, and lastly the La-Angler Lava Lord ruled the underground sea of magma.

There are natural portals deep underground of the mountain that act similar to the [Gate] spell that connects the area with the underground caverns of the Azerlisia Mountains. It allows magma pools to flow between the two locations. At the same time, it was how the three rulers like the La-Angler Lava Lord had been able to travel from one location after another.

The Craftsman of Dwarf Arc
One of the Three Rulers, the La-Angler Lava Lord was swimming in the Land of Molten Magma unbeknownst to Ainz Ooal Gown and his comrades who flew overhead.

Strength
So far, only one of these monsters have been shown. However, it should be noted that the strength among them can vary as each are a unique monster that has adapted to their own environment.

Known Members
These were the three rulers of Mt. Rappaslea, as linked by the [Gate]:
 * La-Angler Lava Lord
 * Phoenix Lord
 * Ancient Flame Dragon

Trivia

 * Based on their name, the three rulers are most likely fire-type monsters due to the environment they reside in.