Speculations So Imu is the Devil King Robin mentioned before

[Sword God Ryuma]

Just like Devil fruits are peoples dreams and desires. Where does their nightmare, pain and anguish manifest too. Thats right Into Imu himself or whatever Devil fruit he ate. Just like Goofy fruit was the Desire of happiness and togetherness. Imu ability or Fruit is Suffering, anguish evil etc.....
Also Seems Oda already told us this when he was releasing Film Red

Probably why people labeled them has "Devil" fruit in the first place because it can bring great Evil like someone like Imu

 

[Salah WG]

I've already said it before, Lulusia Kingdom didn't Explode, it was more like Absorbed
Imu's Ability allow her to extract Desires from People's Wealth (Heavenly Tribute's True Purpose)

However, Imu can only use her Ability on those who willingly give their Wealth/Treasures
If She wants to Enforce it, then a Condition must be met (Similar to how Soul Pocus required Fear), Imu's Ability is related to Loyalty
In other words, Imu can enforce her Ability on those who betray her (Such as Lulusia Kingdom)

Basically, joining WG is like making a Deal with The Devil, it's a Loss-Loss Situation
And this Ability is hinted by the fact that there are 16 Light Beams which Reference Theory of 16 Basic Desires
(Imu is extracting 16 Type of Desires from everything they Own or Treasure)

Process of creating DFs requires other components but overall it all starts with those Extracted Desires.

 

[Warchief Sanji D Goat]

Imu's DF is Devil Devil no Mi.

 

[Fn Lucci]

The tail was a bit... well, the devil thing felt obvious. Personally I've been invested in the first clue, the eyes, as a connection to say that it's Doflamingo Emu. But clearly the Hell Chicken is someone else