Imu

Im is an extremely high-ranking figure in the World Government who sits on the Empty Throne and whom even the Five Elders bow to.

Appearance
Im has a humanoid figure with a hand resembling that of a human's, and eyes that closely resembles, if not identical to those of Mihawk's. He or she wears a very tall crown on their head with long spikes, as well as an extremely long robe that stretches a great distance behind them.

Personality
Little is known about Im's personality. He or she seems to be calm and gentle, as shown when they were handling butterflies in the Room of Flowers. However, Im may actually be more temperamental than he or she seems, as Im appears to bear some form of grudge or hatred towards those who bear the initial "D." as well as the "Mermaid Princess" Shirahoshi, as Im used a knife to cut the bounty posters of Monkey D. Luffy and Marshall D. Teach to pieces then used the same knife to stab a picture of Shirahoshi.

Abilities and Powers
The full scope of Im's abilities are unknown, but the fact that they sit on the Empty Throne, a seat whose occupant would be associated with sole authority of the entire world, and the fact that the Five Elders, who are publicly considered to be the highest authorities of the World Government, bow before them and address them with a great honorific would indicate that Im has the greatest known authority within the World Government.

Weapons
Im possesses a saber. They have not been seen using it in combat, but did use it to cut apart several bounty posters.

Reverie Arc
Im went to a chamber deep within Pangaea Castle on Mary Geoise, where they approached a large straw hat while carrying some bounty posters including Monkey D. Luffy's. Later, they went to the Room of Flowers, where they cut apart Luffy's and Blackbeard's bounty posters while also examining pictures of the princesses Shirahoshi and Nefertari Vivi. Im was then summoned to meet with the Five Elders, and they sat on the Empty Throne as the elders requested that Im reveal the name of the "light" that needed to be extinguished from history.

Trivia

 * Im is the name of a giant appearing in Norse mythology.