All attacks against a blinded character get +2 dice. All actions taken by a blind character are at +2 diff. Blind-Fire is purely random. Certain powers mitigate or even negate this penalty.
Blind-Fighting can be rolled instead of Melee or Brawl, though no more Blind-Fighting dice than you have in the appropriate category. This roll will not receive the +2 penalty.
If a target takes a number of levels of damage after soak greater than their Stamina (For Mortals, and unaugmented Mages, Sorcerers, Thralls, Kinfolk, Kinain, Demons who are not Apoc, and Changelings who have not called down the Seeming) or Stamina +2 (Vampires, Ghouls, Augmented Mortals, People on Smack, Apoc Demons, Changelings with their Fae Mien revealed, Shifters in any form, KotE), they are dazed and must spend their next turn shaking off the attack's effects.
Add two dice to all rolls to attack an immobilized but still struggling target. Attacks automatically hit with full successes on a target that is 100% immobilized.
The victim falls down. Victim immediately rolls Dexterity+Athletics, if successfully, they -immediately- get back up, but has Init reduced by 2 for the next turn. On a failure, they stay down, and can use an action to get up when they next have one available. On a botch, not only do they suffer the effects of failure, but take an immediate level of bashing damage.
Maneuvers like Tackle and Sweep are meant to cause knockdown, but a sufficiently powerful attack of any kind may cause it. Up to the ST, but my suggested rule of thumb is any attack delivering 5+ levels of damage before soak has the potential to knock someone down if it's got Kinetic Force behind it.
Someone fighting against multiple opponents in close combat is at a severe disadvantage. All attack and defense rolls suffer a penalty of +1 difficulty -per opponent after the first- to a maximum of +4 diff when fighting against 5+ foes at once. Even Elder Vampires and Ahroun can be brought low by the sheer press of bodies.