Vader and Palpatine both have abilities that offer a benefit to/for Empire, and separately to/for Sith.
Palpatine and Vader are the only toons who are both Empire and Sith.
As such, Vader is the only other toon who can fully benefit from Palpatine's leadership, and Palpatine is the only other toon who can double boost Vader's speed.
Replies
Palpatine and Vader are the only toons who are both Empire and Sith.
As such, Vader is the only other toon who can fully benefit from Palpatine's leadership, and Palpatine is the only other toon who can double boost Vader's speed.
They have unique synergy with one another.