10 Doctor Who Villains Who Should Return For Russell T Davies' New Series 14
6. The Krillitanes
The fact that The Krillitanes haven't returned to Doctor Who since their first and only episode is bizarre. Debuting in David Tennant's first season, The Krillitanes are a race of beings who take physical aspects from the races they conquer. This means they can look like practically anything, as shown when they look to be human.
What makes The Krillitanes such an awesome enemy is the lore that surrounds them. In their one episode, they are built up as a race that can go head-to-head with the Time Lords, and The Doctor even recalls a previous encounter he had with them.
There is a lot of mythology that could be mined from this enemy, and they also offer the unique ability of changing what they look like. They don't have to look like the bat-like creatures fans caught a glimpse of in 2006. Instead, they could be new or could have taken aspects from aliens we've met before.
There's a lot of mileage with The Krillitanes, more so than some of the other enemies from the Davies Era. If he needs to bring back one creature from his era, it should be these!