There's already been one multiplayer beta for Halo Wars 2. Now a second is coming up prior to the game's launch on February 21st.
This time the beta will focus on the new card-based mode 'Blitz.' In Blitz mode players use deck-building alongside the game's tactical RTS combat, combining one of the biggest trends in modern gaming with, well, a style of game that's not nearly as popular as it once was.
The beta runs from the 20th to the 30th of January---so a good, long time to get familiar with this game mode, which I'm betting Microsoft is hoping will be a big hit. This late in the game---just one month out from launch---a beta serves as a stress test for servers and as a demo/hype-builder for gamers.