The Seeker is a variant of the Impostor who appears in the Hide n Seek mode of Among Us. the Seeker, has to kill Crewmates who are hiding throughout the map. The seeker is visually distinguished from the Crewmates, having a permanently open mouth with a wiggling tongue. During Final Hide, the Seeker gains a speed boost. In April Fools, the Seeker is replaced by the Rancher.

More facts here: https://among-us.fandom.com/wiki/Hide_n_Seek