This world.....

The secret boss Zenithega is accessible by purchasing Third Eye from the shop for 10,000 Souls which can be obtained by defeating Sagat. After equipping Third Eye in your item slot, press 'X' twice to use it, then go to the Sagat arena.

I do not think this boss is possible at the moment. Some of the attacks in phase 2 seem impossible to do and overall the boss feels unpolished and rng dependent. Maybe we are the testers? MIND BLOWN

Anyways, I will wait for a nerf or something. Publishing this video now as I will be busy in the next couple of days :)

Btw the sprite for this boss is based on Satori Komeiji from Touhou Project.

Timestamps:
0:00 - Obtaining Third Eye
0:57 - Phase 1
5:09 - Phase 2 Attempts

Link to Game: https://www.roblox.com/games/11684369582/I-Wanna-Test-The-Game
The game that this is based off of: https://cwpat.me/fangames-intro/