They were attempting to transport Lee, Tina and Barrage to Coral Grove so it can be reasoned they are related to Coral Grove and/or The Council in some capacity. They were able to defeat Barrage, a former military general, indicating they are capable fighters.
Their suits resemble the hazmat suits worn by the Cleaners, with their masks in particular having similar designs.
Assumabley, they were made Finwich (due to looking like the hazMats), and work for the Council. There are also Blue ones who are presumably under the control the Experts. As well as Red Reaper Matts under the control of His Eminence.
Each different type of the reaper mat seem to have different traits. The green ones are equipped with scythes, the blue ones can cause head pains, and the red ones are able to create small energy shields. The green ones can fly, while the blue and red ones seem to only be able to hover.
The Dance Part 2 (Green)
Return of the Ping (Green)
Misadventures in Babysitting (Green)
Fence O Palooza (Green)
The Outcasts strike back (Green)
Fight or Flight (Green)
Follow that Finnwhich (Green and Blue)
Mummy Ping and the snake man of evil (Blue)
Game of Clones (Blue)
Band of heroes (Blue)
From bad to wurst (Green and blue)
mannifestum rising (blue)
date with destiny (blue and Debut Of The Red Reaper Mats )