Hostility

Hostility is the reaction opposing ships have to encountering your vessel in the void. Perhaps counterintuitively, A positive hostility indicates a friendly reaction to your ship, while a non-positive one indicates some level of aggression. Each ship captain type will behave differently at different levels of hostility. Not only will some ships take actions in the Ship Encounters phase, such as accepting your bribes or surrender, but the AI used if you enter Ship Combat with them will also be different depending on hostility. Hostility can shift between -5 and +5. In rare cases, you can have even worse than -5 hostility but it has no impact on gameplay.

The following are factors that can set your initial hostility:
 * Captain's faction reputation (both local and with the opposing ship's faction)
 * Whether the Captain's faction is in a conflict with the opposing ship's faction (and what kind of conflict)
 * What rumors are active in the quadrant
 * Orbital operations will also consider the kind of operation you were taking into the hostility equation (Blockading, Spying are hostile, Patrolling is friendly)

The following are factors that can modify your hostility before/outside of combat:
 * Bribing your foe (+1 Hostility, unless you are extremely negative with the opponent's faction)
 * Many "encounter" talents
 * Demanding Tribute (-1 hostility, always)
 * Using Flash Charge to enter combat (-2 hostility)

The following are factors that can modify your hostility in ship combat:
 * Dealing damage to the ship (-2 Hostility)
 * Boarding the ship (-2 Hostility)
 * Preventing the foe from escaping (-1 Hostility, unless coupled with advancing on the foe, in the which case it is +0)
 * Advancing on the foe (-1 Hostility)

Enemies use different AI depending on the hostility level during a given turn. The biggest changes, however, are whether they will take any offensive action against you at all:

This gives a serious advantage to the player if well understood. If a Pirate ship is encountered at -2 hostility, you could bribe once to reach -1 hostility. This would give you a free turn to attack and buff yourself before the pirate returns fire. You can do even more with extremely positive hostility. A Merchant at +5 hostility could have tribute demanded of it three times (the maximum), and then enter combat at +2 hostility. This would let the player advance on them while buffing his/herself up to range 2 before the merchant ship would decide to start firing on the ship they trusted oh so much. If you didn't demand tribute, you could actually range change to range 2, fire a gravity cannon at their ship, and advance once more to boarding position 1. The opposing crew would simply assume it was a misfire and that they surely wouldn't be betrayed by their faction's hero.