[Solved] Fully clear the Harvest - Impossible ?

Hi,

I just tried to clear the Harvest but i've only 1 mob remaining and it seems to be a "frog pet", released when you kill one of the 3 bosses... I walked in the map 4 more times to be sure no mob was there and it's the case. The only one left is this untargetable frog.
Is this a bug or there's something special to do ?
Screenshot 1 - BR #3 673 976 400
Screenshot 2

Edit : Solved, you need to go in the black core as it's the same area and kill Malachai.

Did you kill Malachai? The Black Core is a section of The Harvest area.

Really ? I thought about it but finally i guessed it was propably another area. Thanks then, i'll kill him a second time.

Edit : Indeed, thanks !

i did encounter the same thing,left 1 remaining before enter malachai's pit.then after i kill malachai becomes 3 remains.was it the 3 hearts become the 3 remains?

it seems there is a bug in merciless difficulty because when i did it in normal, i got the achievement completed!i did it 3 times in merciless and didn't come to mind to do it in other difficulty.