The Coral Palace is a location first introduced in Monster Hunter Rise. It is exclusively used for the battles against Thunder Serpent Narwa, Wind Serpent Ibushi, and Narwa the Allmother.
There are two levels to the Coral Palace; the upper level is only accessible via Wirebug, and is surrounded by several temple-like buildings. The arena was once likely submerged in the past, as coral and seaweed can be seen covering the surrounding rocks and buildings. Various Rampage installments, such as cannons, a Dragonator, and a Splitting Wyvernshot, are scattered throughout the arena. When fighting Thunder Serpent Narwa, the arena is bathed in a yellow light; when fighting Wind Serpent Ibushi, the arena is bathed in a blue light and a strong wind will blow around the arena.
Upon defeating Ibushi, the floor will cave in and Ibushi, as well as the hunter, will fall to the lower level. This level appears to be a sort of nest, with branches scattered throughout the cave. The cave is bathed in a purple light, which becomes stronger once Narwa absorbs Ibushi's life force and achieves her Allmother form. The Rampage installments from the upper floor have also fallen down - while the hunter can still use smaller weapons against Narwa, the Wyvernshot is unable to be used and the Dragonator is now wielded by Narwa herself.
During the battle against the Allmother, a powerful monster will appear and do battle with her, allowing the hunter to ride it. When fighting the Allmother for the first time, this monster will always be Magnamalo, or Malzeno in Master Rank. Once the hunter has defeated the Allmother, future fights will introduce the possibility for Kushala Daora or Teostra to appear in their place.