In 5e if I were to have two daggers from the magic item bracer of flying daggers witch says (As an action, you can pull up to two magic daggers from the bracer and immediately hurl them, making a ranged attack with each dagger.) can I with the secondary arms of a thri-kreen which can wield a weapon that has the light property, create/throw those daggers as well as create/throw the soul knife in one of the remaining hands that are free as the same attack action?
The idea for the build (as you’ve probably already figured out) is to throw two daggers, creating/throwing the 1d6 soul knife, and then bonus action create/throw the 1d4 soul knife for a total of four attacks. Dip into fighter for the Thrown Weapon Fighting Style for a +2 to damage roles for 3d4 and 1d6 + modifiers, sneak attack, and then do it all over again with action surge minus the bonus action attack.
Short answer ... No. Extra arms don't give you extra actions. The psychic blades need the attack action which you wouldn't have if you use the bracers as an action. If you multiclass, you could get action surge from being a fighter and use it that way. That would only be once per short rest though.
There are a number of issues with this plan and I will try to explain all of them but the short answer is 'no'.
1) As Lathius explained Physic Blades requires you to take the Attack Action to create and attack with the 1d6 blade. In order to get the bonus action 1d4 blade you must first take the Attack Action and attack with the 1d6 blade. The Bracer of Flying Daggers also requires your action, but this is an action granted by the magic item, not the Attack Action. You only have one action per turn do you cannot do both. Action Surge and the spell Haste are workable solutions to this issue though.
2) The psychic blades manifested have the Finesse and Thrown properties, but not the Light. This means to use them a Thri-kreen would need to use their primary hands to wield them.
3) Sneak Attack can only proc once per turn. Action Surge grants you a second action but it is still the same turn so you could still only proc Sneak Attack once. If you want to proc Sneak Attack more than once per round it is possible, but requires finding a way to attack with your reaction. This is harder for a Soulknife since they need to keep their hands free to manifest their psychic blades. Consequently most reaction attacks they might get must be Unarmed Strikes since they aren't wielding a weapon and can't proc Sneak Attack.
*Edit* I know it's not what you had in mind but take a look at the Dart. It is a unique weapon that can stack Thrown Weapon Fighting Style, Archer Fighting Style, Sharpshooter, and Crossbow Expert (including triggering a bonus action attack with a hand crossbow).
While Thri-Kreen's Secondary Arms let you wield a weapon, it doesn't give you an additional action to do so and therefore you can't do any attack with them when using an action to use your Bracers of Flying Daggers unless you can take an additional action on your turn with a feature such as Action Surge to attack with a dagger but you'd be better off using the additional action to use the Bracers of Flying Daggers again in this case.
Psychic Blades lack the light property so they can't be welded with your Secondary Arms and also they use the Attack action, which is a different action than the one required to use some Bracers of Flying Daggers. So they're incompatible, you're either using the Attack action and bonus action to attack with Psychic Blades or you;re using your action to attack with Bracers of Flying Daggers.
*Edit* I know it's not what you had in mind but take a look at the Dart. It is a unique weapon that can stack Thrown Weapon Fighting Style, Archer Fighting Style, Sharpshooter, and Crossbow Expert (including triggering a bonus action attack with a hand crossbow).
Just curious what would be the advantage of using dart over hand crossbow? You'd need a second Fighting Style to deal 1d4+2 while the hand crossbow does 1d6 with better range
*Edit* I know it's not what you had in mind but take a look at the Dart. It is a unique weapon that can stack Thrown Weapon Fighting Style, Archer Fighting Style, Sharpshooter, and Crossbow Expert (including triggering a bonus action attack with a hand crossbow).
Just curious what would be the advantage of using dart over hand crossbow? You'd need a second Fighting Style to deal 1d4+2 while the hand crossbow does 1d6 with better range
Oh, I was coming from the position of "If you already have the Thrown Weapon Fighting Style consider these other options". Archery is by far the better fighting style on its own. Darts are interesting because they allow for some unusual combinations.
In 5e if I were to have two daggers from the magic item bracer of flying daggers witch says (As an action, you can pull up to two magic daggers from the bracer and immediately hurl them, making a ranged attack with each dagger.) can I with the secondary arms of a thri-kreen which can wield a weapon that has the light property, create/throw those daggers as well as create/throw the soul knife in one of the remaining hands that are free as the same attack action?
The idea for the build (as you’ve probably already figured out) is to throw two daggers, creating/throwing the 1d6 soul knife, and then bonus action create/throw the 1d4 soul knife for a total of four attacks. Dip into fighter for the Thrown Weapon Fighting Style for a +2 to damage roles for 3d4 and 1d6 + modifiers, sneak attack, and then do it all over again with action surge minus the bonus action attack.
I just want to throw a hurricane of daggers
Short answer ... No. Extra arms don't give you extra actions. The psychic blades need the attack action which you wouldn't have if you use the bracers as an action. If you multiclass, you could get action surge from being a fighter and use it that way. That would only be once per short rest though.
There are a number of issues with this plan and I will try to explain all of them but the short answer is 'no'.
1) As Lathius explained Physic Blades requires you to take the Attack Action to create and attack with the 1d6 blade. In order to get the bonus action 1d4 blade you must first take the Attack Action and attack with the 1d6 blade. The Bracer of Flying Daggers also requires your action, but this is an action granted by the magic item, not the Attack Action. You only have one action per turn do you cannot do both. Action Surge and the spell Haste are workable solutions to this issue though.
2) The psychic blades manifested have the Finesse and Thrown properties, but not the Light. This means to use them a Thri-kreen would need to use their primary hands to wield them.
3) Sneak Attack can only proc once per turn. Action Surge grants you a second action but it is still the same turn so you could still only proc Sneak Attack once. If you want to proc Sneak Attack more than once per round it is possible, but requires finding a way to attack with your reaction. This is harder for a Soulknife since they need to keep their hands free to manifest their psychic blades. Consequently most reaction attacks they might get must be Unarmed Strikes since they aren't wielding a weapon and can't proc Sneak Attack.
*Edit* I know it's not what you had in mind but take a look at the Dart. It is a unique weapon that can stack Thrown Weapon Fighting Style, Archer Fighting Style, Sharpshooter, and Crossbow Expert (including triggering a bonus action attack with a hand crossbow).
While Thri-Kreen's Secondary Arms let you wield a weapon, it doesn't give you an additional action to do so and therefore you can't do any attack with them when using an action to use your Bracers of Flying Daggers unless you can take an additional action on your turn with a feature such as Action Surge to attack with a dagger but you'd be better off using the additional action to use the Bracers of Flying Daggers again in this case.
Psychic Blades lack the light property so they can't be welded with your Secondary Arms and also they use the Attack action, which is a different action than the one required to use some Bracers of Flying Daggers. So they're incompatible, you're either using the Attack action and bonus action to attack with Psychic Blades or you;re using your action to attack with Bracers of Flying Daggers.
Just curious what would be the advantage of using dart over hand crossbow? You'd need a second Fighting Style to deal 1d4+2 while the hand crossbow does 1d6 with better range
Oh, I was coming from the position of "If you already have the Thrown Weapon Fighting Style consider these other options". Archery is by far the better fighting style on its own. Darts are interesting because they allow for some unusual combinations.
Aye i see where you're coming from.