Caladbolg's seal is a seal made by Regis Nex to seal away Caladbolg. When the seal is released, a younger version of Caladbolg appears. There are two seals; one is in Thanatos and the other in Serphent. Both of the seals were undone by Xix's blood, however, the current location of the two parts in unknown as well their status. While sealed, both seals emitted a sinister aura.
In order to release the seal, a royal's blood is needed. This blood needs to come from the royal's heart.
ThanatosThe seal in Thanatos is located deep in an underground prison. The prison has many layers of protection; the first being a seal at the very entrance, the second on the bottom floor of the prison and lastly the real seal which seals away Caladbolg. All three seals have to be undone by a bearer of the royal blood.
Caladbolg's seal in Thanatos has a wing sticking out of the floor. The wing belongs to Caladbold and is the only visible trait of the seal.
When the Night clan captured both Xix and Miya in order to undo the seal, Miya was the one who opened the fist two seals while Xix was the one to open the last seal. In order to open the last seal, the blood has to come from the royal's heart. Due to Xix being an undead, he has survived this process.
Caladbolg's seal was broken and Caladbolg was freed. He escaped with the help of One who along with Seon Yu came to rescue him. After their escape, Regis Nex took his daughter Miya and Xix to the castle.
SerphentCaladbolg's seal in Serphent resembles the one in Thanatos in a way that it is sealed deep underground as well. In order to find the seal itself, a guide who knows the way is needed, otherwise anyone who seeks the seal would be lost forever.
The seal itself resembles a tube which contains Caladbolg inside. Caladbolg is surrounded by roots with thorns which are a part of his power. When Xix used his blood as a medium to perform a ritual to save Yuan's life, Caladbulg slightly awakened due to sensing the Regis blood. When Ninoorut Noah arrived with Siana, Xix's blood was spilled and Caladbulg was released.