Niantic has been bringing back all the hits in December, making sure trainers have one last opportuinty to capture anything they may not have previously in the year. Or maybe it's because they want to make sure people are logging into 
Pokemon Go even though they are tucked in their warm homes this Winter. Either way, the evidence surmounts. Research Breakthroughs for Legendary Birds and Beasts and the December Community Weekend Event helped to show this and now the we have the returning Ghost Raids.
Out of all of the Pokemon that are available now, two of them - Tyranitar and Machamp - were already available, and the rest are new to rotation. Many of the Pokemon are ghost types and more than half of the list has shiny versions available as well, with a majority of the shinies also being Ghost Types. Those are Mawile, Shuppet, Duskull, Shinx, Snorunt, Gengar, Pinsir, Absol, Sableye, Snorunt, and Alolan Marowak.
Below you will find a full list of the current available Raid Bosses in 
Pokemon Go.
Tier 1
	- 
		Drifloon
 
	- 
		Shuppet
 
	- 
		Snorunt
 
	- 
		Shinx
 
	- 
		Buizel
 
Tier 2
	- 
		Sableye
 
	- 
		Mawile
 
	- 
		Sneasel
 
	- 
		Misdreavus
 
Tier 3
	- 
		Gengar
 
	- 
		Machamp
 
	- 
		Pinsir
 
	- 
		Sharpedo
 
	- 
		Scyther
 
	- 
		Alolan Raichu
 
Tier 4
	- 
		Alolan Marowak
 
	- 
		Houndoom
 
	- 
		Tyranitar
 
	- 
		Absol
 
Tier 5
	- 
		Cresselia
 
	- 
		Deoxys (EX Raid)
 
With this information, will you be chasing any shinies? Let us know below!