Another game mechanic that is called shuffle building. Some could say it is an off shoot of deck building mechanic that is very popular.
You take 2 or more decks of cards and shuffle them together to make a deck that you play with in the game. So one deck is a faction with strengths and weaknesses and the other deck is another faction and you put them together using their combined strengths and weaknesses. You want to offset one faction's weakness with the other faction's strengths.
Smash up is a game that uses the shuffle building mechanic. It is not the first shuffle builder, but it is a successful one. You take two 20 card decks of different factions and put them together into a 40 card deck you use to conquer bases against your opponent. For instance, The pirate faction can move their minions from one base to the next. The Zombie faction can bring back minions from the discard pile back into the game. So you can use the pirate ability to move Zombie minions that was just brought back into play to other bases and overwhelm them.