An unnamed Zygon was part of the group stuck on Earth. Their ship landed in 1562, but the group retreated into a statis chamber and stayed there until 2013, where this Zygon took Osgood's form. She went down to the lower levels, where she ambushed the real Osgood and took her inhaler.
In the Under-Gallery, the Zygon attacked Clara Oswald, but fell back when the latter got hold of a vortex manipulator. Later, three of the Doctors erased the memories of both the humans and their Zygon counterparts, and peace was restored. (TV: The Day of the Doctor)