Arcturis

Arcturis is a level 74 spirit beast found in Grizzly Hills. He's one of the 6 Spirit Beasts known, and is the first Spirit Beast to have the look of a bear.

Trivia
The name Arcturis is likely inspired by the name Arcturus, the name of the brightest star in the constellation Boötes, which in turn is derived from the Greek word άρκτος, meaning "bear".

Arcturis is on a 21 hour spawn timer that begins from time of kill/tame. This timer DOES reset with server downs and maintenance days.

Note
Despite being a rare creature, Arcturis is not on the list of creatures needed for the achievement.