Terra Nivium 20,000 B.C.
|Overcoming the Terra Nivium 20,000 B.C.||Beat the Terra Nivium 20,000 B.C.||x100|
Hokishi Forest 
Skills: Terra Nivium 20,000 B.C. (Hidden Boss)
|Starts battle with another Artificial Spirit with its corresponding Zone
Summoned Artifical Spirits follow their respective move patterns.
Summons another Artificial Spirit every 6 turns
|HP stopper at 50% HP. Summons another Artifical Spirit with its corresponding Zone|
|-||Optic Axis||Type and Physical Resistance Buff on all allies|
|-||Planetar||Magic attack on single enemy|
|-||Phonon||PWR+INT buff on all alllies|
|-||LINER||Fixed 2000 damage on all enemies|
|-||Fifth Force||Counter all non-crystal attacks with Quintessence|
|-||Quintessence||(Counter) Magic attack on single enemy|
How to find Terra Nivium 20,000 B.C.
To unlock this battle, you will need the "Spirit Detector". This can be found in Spirit Sanctuary after completing the Zerberiya: Sword and Wings Mythos: Song of Sword and Wings of Lost Paradise Mythos, chapter 8. Go back to the boss room and check the hidden room on the far right (now accessible due to collapsing pillar).
Terra Nivium 20,000 B.C. itself can be found in its own area in Hokishi Forest. If you enter Hokishi Forest from Gadaro with the Spirit Detector item, you will cause the entrance to this area to appear at the first fork in the path. The entrance is located near the southern end of Hokishi Forest.