I understand how linked nodes work. They are purple arrows where one end is the source of the boost, and the other end where the arrow is pointing to is the receiver of the boost.
In the image below we can see a droid boosting Ultron (the big boss). If someone kills the droid, the boost is removed making it much easier to defeat Ultron.
What I don't understand is those orange circles around bosses. For example, in the image below Ultron also has an orange boost. What are those boosts? Who is the source? And is it possible to remove them?