This update adds combat to the game (combat is mostly optional at this point, however).
In keeping with the general theme of 'humans are mostly good' in the game, the player is limited to researching and building a stun blaster, which can drive off hostile aliens or knock them unconscious, but won't kill them. The blaster can not be used on harmless non-hostile creatures.
The update also introduces several new alien species/factions, all of which can become a bit 'fighty' at times.
Given the large amount of related systems work required to get combat working in the game, there are some loose ends and polish that still needs to be done. There will probably be a followup update soon that addresses these issues and fixes any bugs discovered in the near future (especially any combat-related bugs).
This update is likely to be the last 'new systems' update for at least a while, with development transitioning over to creating new content that uses the various new game systems that have been added to the game in the last year or so.