The Mighty Leviathon!
With Eliana's help in the form of the magic gadget that she brought; the Space Beast hunting mission just became a lot more important to Sebastian.
With the incredible utility of this magic gadget, he just couldn't fantom how valuable it actually was. He was grateful for her help.
With the Codex Suppression, the Space Beast could be temporarily suppressed to the purple tier realm, thereby making Sebastian alter his plans since he could now take the hunt personal.
Against a Red tier predator, Sebastian stood no chance not to talk of when this predator was a Space Beast to boot.
But if this Space Beast was a purple-tier predator, Sebastian would be damned if he didn't claim the opportunity to battle this worthy opponent.
Since evolving to the purple tier realm, Sebastian had fought some equal-tiered opponents, but none of them have managed to give him a challenge.