Eternal Star can be obtained from a Styling Gift Box after completing Oath of Honor.
A headless body, of course, wearing Undead Light, Morning Star, and Invincible Trip. The body is in a sitting position, the left arm putting a hand on the neck while the right caries Hope Blade.
Eternal Star is part of an alternative version of the North suit Oath of Honor.
The other parts of this suit are Sacred Song of Snow, Flower of Wishes, Glorious Light and Unspoken Oath.
The original version of the suit contains Golden Chapter, Undead Light, Morning Star, Invincible Trip, Flower of Wishes, Fate Reversion, Hope Blade, Glorious Light and Unspoken Oath.