The Mire filled the classic Who role of ‘Alien creating menace to give reason for Doctor to meet/save interesting person. They filled it admirably well clonking around in metal suits and had a pretty original look under the hood
The Mire were a warrior race active in the 9th Century. They travelled across space, conquering Planets and assimilating their technology and the biological essence of their warriors to advance their own campaign.
Seemingly straight out of the 90s BBC Narnia costume department this was a race I couldn’t take seriously at all. They filled the role the Mire took but nowhere near as well.
Leonians were a race with advanced capabilities including the creation of portals across vast distances off space. They were also ruthless, punishing failure with death among their own kind