Invasion is an original game created specifically for Solavant. I like this game mostly because it is unlike any other solitaire game I've played. The card movements are difficult and tedious to play on a table with real cards, but with Solavant this tedious movement is automatic. The metaphor for this game is of protecting an ancient land from an invading army by subverting the invaders to your side before they cross the sea.

The rules may look complex at first glance, but they are actually simple once you've played a few times. The goal is to build the foundations on the right from Aces to Queens regardless of suit. (The rules incorrectly state Aces to Kings, this will be corrected in the next version.) The foundations are the Homeland that you must protect from the invading Army.
The four Kings on the left are not in play. They represent the invading leaders and are just for show.
Between the Kings and Homeland are rows that make up the Sea. Cards of the Army are dealt 4 at a time from the stock pile into the rows at the leftmost side. Any cards already in the rows are automatically moved to the right one space as they sail closer to the Homeland. If any of the four rows is completely filled, cards cannot be dealt from the stock.
The rightmost card of any row may be built onto any foundation pile that can take it. This is the "subversion" process.
Only one move is allowed within the Sea rows. If the rightmost card of a row has a space beside it, you may move a card that is one lower in rank into the space. The card you move can be any card in the Sea. The gap from the moved card is automatically closed leftward, except if the gap is the leftmost space in a row, then it is filled from the stock.
The game is lost if any row is completely filled and you cannot create gaps in it because no more cards can be dealt from the stock. The Army will have successfully invaded the Homeland.