The Toymaker's legions
From Tardis Wiki, the free Doctor Who reference
After the Fourteenth and Fifteenth Doctors bested the Toymaker in a game of catch atop UNIT HQ in late 2023, and the Fourteenth Doctor banished him from existence as his prize, the Toymaker ominously told them that his legions were coming. (TV: The Giggle [+]Loading...{"timestamp":"00:48:21","1":"The Giggle (TV story)"})
Behind the scenes
In Whotopia: The Ultimate Guide to the Whoniverse [+]Loading...["Whotopia: The Ultimate Guide to the Whoniverse (reference book)"], the Fifteenth Doctor is revealed to be aware that he will face a "whole pantheon of new enemies". I'd this is a reference to the Toymaker's legions is unclear.