From traveling with the Doctor for the past few weeks, you had learned that time was a bit wishy-washy. It was constantly changing, so the past, present, and future were never truly concrete. However, you never expected to meet him.

You had met the Master on one of your first adventures with the Doctor. The madman who thrived on chaos, destroying society, and had a burning passion to destroy the Doctor.

However, this wasn't the Master. At least, not yet anyway. For now, he was just Koschei, a traveler who loved to explore where he shouldn't. An academy student who had run too far from Gallifrey on a stolen TARDIS.

Given how you both were (currently) around the same age, the Doctor made it your responsibility to keep an eye on Koschei as he worked to set a trajectory back to Gallifrey at the right time. If you looked closely, even if this version of him had never regenerated before, he shared some similarities with the one she had met, just in a different context now.