Google's Ngram Viewer suggests references to "vassals" have been in steady decline for almost two hundreds years, yet Google Trends suggests a doubling or even tripling of interest over the past twenty. The culprit can be found among the "related topics" list at the bottom, which includes Crusader Kings 2 and Europa Universalis 4.
The relentless PR campaign in favour of feudal obligation continues in the next Stellaris expansion, Overlord, which will add new "vassalization mechanics" when it launches on May 12th.
Here's the release date announcement trailer:
"Use new vassalization mechanics and specialize your subjects into economic powerhouses, defensive bulwarks, or technological masterminds," says Paradox's release date announcement post. "Negotiate the terms of your subjects’ Vassal Contracts, with the ability to subsidize their income, restrict their expansion, construct buildings on their worlds, and more."
Adding space vassals among the space vessels makes sense, because Paradox's grand strategy games are at their best when the consequences of your actions are a mixture of terrible warfare and the much greater terror of a person not liking you quite so much anymore.
Overlord also adds new Origins, including the ability to begin as the "subject of an advanced AI". There are a lso three new Megastructures, including the planet-hugging Orbitan Ring, self-explanatory Quantum Catapult, and a Hyper Relay network for ferrying fleets and resources about your empire.
As previously announced, Overlord will ship alongside a new free update, version 3.4.
Stellaris: Overlord will release on May 12th on Steam and will cost £15.50/$20/€20.