For those who have played on a MUD before, combat on Haven will be quite familiar. The difference on Haven is that behind the scenes, it uses d10 based combat from the Storyteller System. For those unfamiliar with MUD combat, the following is a brief guide. (Note: Currently the d10 style combat system is only for Player characters; d10 combat for NPCs is under development.)
There are a number of ways to initiate combat, the simplest being to simply type 'kill' then the name of your target. For example, 'kill peasant' or 'kill Henry'. There are also a number of skills that will initiate combat, such as backstab, kick, bash, etc. Once combat is initiated, it will proceed automatically with one 'round' of combat occurring approximately every 3 seconds. Each round includes all of the hits the player makes against their target, and all of the hits the target makes against the player.
Each round is a collection of singular 'hits', each computed individually. Each hit follows the same basic routine. Dexterity and either Brawl (for unarmed) or Melee (for armed) are added together to form an attack roll. If this succeeds, the aggressor's Strength plus any modifiers are combined to form a Damage roll. The victim rolls soak and armor, which subtract from the damage successes. If any damage successes remain, they are multiplied by a modifier and applied as damage.
When damage is taken, it is deducted from the character's Hit Points. If a character's Hit Points are reduced to zero, non-vampire characters die while vampire characters go into a state of torpor in which they must be beheaded to fully kill them. Once the target is killed, experience is calculated and awarded to each group member in the room.
For a more expansive and technical breakdown, refer to Combat (Technical).