EDIT.
NWN Wiki wrote:A flurry is effectively the smallest unit of time used by Neverwinter Nights, as far as players are concerned. Each flurry lasts two seconds, so there are three flurries in a round. All combat actions taken in a single flurry are essentially resolved simultaneously. In particular, all attack rolls for a given flurry are resolved before the damage from those attacks is calculated and applied. (This is known to reduce the importance of initiative.)
Due to game engine limitations, the maximum number of attacks per flurry by a single character is 5, which translates into 15 attacks per round. This is sufficient most of the time since a character can have at most 10 normal attacks per round. However bonus attacks, such as a cleave attack or an attack of opportunity, can meet or even exceed this game engine limitation.
Attacks per round are distributed as evenly as possible among the three flurries in a round, as shown in the following table.
NWN Wiki wrote:Death Attack
Specifics: At first level, an assassin may use a death attack, which functions similarly to a sneak attack in that if the target is not in combat they become victim to the death attack. The successful attack forces the target to make a fortitude save or become paralyzed. Even if they succeed with the saving throw they still suffer +1d6 points of damage in addition to the normal damage the attack caused. This damage increases to 2d6 at level 3, 3d6 at level 5, 4d6 at level 7, and 5d6 at level 9.
Use: automatic
Notes:
Death attacks are made whenever an assassin would qualify for a sneak attack, regardless of the target's combat state. (If an assassin also has a sneak attack, the game only reports "sneak attack" to the player.) In particular, death attacks can be made with ranged weapons if within 30 feet of the target.
All death attacks deal bonus damage, but not all death attacks trigger a paralysis save.
The bonus damage stacks with that for sneak attacks, including the blackguard's sneak attack.
As with sneak attacks, the bonus damage is not multiplied in the case of a critical hit.
A death attack only triggers a paralysis save if the target is not engaged in combat, as per this feat's description.
As all attacks in a flurry are effectively simultaneous, there will be a saving throw for each attack in the opening flurry of combat.
The difficulty class of the saving throw is 10 + assassin level + intelligence modifier.
This will apply triggering the paralyzing attack on your enemy as far as he still out of combat.
I guess you will deliver four death attacks before the combat starts for your foe after your surprise flurry of four (the "first attack").
NWN WIki wrote:the only way you are going to paralyze someone with death attack is if your target is flat-footed.
NWN Wiki wrote:
Flat-footed:
A character or creature that is caught unawares or otherwise unprepared is considered to be flat-footed. A flat-footed character loses his dexterity, dodge, and tumble bonuses (but not the penalty for a negative dexterity modifier) to armor class (AC) and cannot make attacks of opportunity, cannot make a defensive roll, and cannot deflect arrows. Furthermore, flat-footed characters are candidates for a sneak attack or death attack. The uncanny dodge and defensive awareness feats allow retention of the dexterity AC bonus when flat-footed, but dodge and tumble bonuses are still lost (as is the ability to make attacks of opportunity, etc.).
A character will be considered flat-footed if attacked by an unseen creature, unless the attacker is heard and the character has the blind fight feat. Being unseen can be the result of blindness, darkness, invisibility, stealth, or (for NPC perceivers) coming around a corner without time for the perception event to fire (a window of at most four seconds). In other circumstances, a character is flat-footed when doing none of the following: attacking (melee or ranged), moving, or casting a spell, feat, or special ability.
In particular, the following conditions preclude those three activities, so effectively cause one to be flat-footed: entangled, stunned, paralyzed, petrified, prone, and sleeping. Furthermore, an empty action queue can cause a character to become flat-footed as soon as they finish moving or casting a spell; after an attack, doing nothing does not cause a character to become flat-footed until a few seconds have passed (indicated visually by equipped weapons returning to their default pose, such as resting on a shoulder for two-handed weapons).
My guess is:
First: You deliver your ten attacks:
1st flurry (4 attacks if you reached 10 per round): Applies death attack triggering paralize.
2nd flurry (3 attacks if "): Don't apply the paralyze but applies the +1d6
3rd flurry (3 attacks if "): Don't apply the paralyze but applies the +1d6
If I am not wrong, your npc foe will riposte starting at your second flurry, after or before depending the initiative.
NWN WIki wrote:Non-playable creatures when ambushed in the first round will repay attack immediately when they are hit no matter of initiative. Due to this fact, their attack flurry may overlap with player and they will attack before player's flurry apply damage, so even if the first flurry should kill them they will be still able to harm character attacking this way.
However the surprise moment applies only for first round. In subsequent round, the initiative start flurries for both creatures arranged per initiative. Flurries in subsequent round doesn't overlap - each flurry will trigger actual damage before creature with lower initiative start her flurry giving the initiative real effect.
