I believe the basics of the attack system will be similar to the AoC mod, meaning that you have three principal attacks with every weapon (for most weapons that was horizontal swing, overhead swing and thrust), each bound to a mouse button. The main difference with AoC would be that you can change the path of your weapon during a swing. You could, of course, already do that in AoC, but this time, it will actually matter. Afaik, parrying will no longer be a magical force field blocking everything in front of you, you will actually have to aim your parries. So your aim combined with the chosen attack direction should give quite a lot of freedom in offence.
Additionally, I believe it was said that stringing attacks together will feel a lot more smooth and organic, which probably means that your character will not just be limited to the three set attack directions. This might mean that if, for example, you just did a right-to-left horizontal swing and quickly tapped the horizontal button again afterward, your character would follow up with a left-to-right swing. This was impossible in the mod, your character always had to reset to the starting position first before attacking again, and attacks were only limited to the three predetermined swings each weapon had.
Please correct me if I'm wrong on any of this.