Thinking ahead, since we probably won't get an official update to the soulknife for years - would you give a soulknife's psychic blades weapon properties? Something like Vex seems obvious. In 5.14, soulknives are pretty competitive despite their PB damage not scaling (but would scaling add that much?). However, with weapon mastery, the PB could get relegated to a backup weapon, as a shortsword/dagger combo could prove more useful, especially once characters start picking up magic weapons.
a) make their blades appear any time they need to use them (examples: Defensive Duelist parry, if they have the Extra Attack feature via multiclass, etc.). Currently, you get 1 Attack action attack with them (no matter how many attacks you get via Attack action; because it appears when you start the Attack action, and disappears as soon as you use it), and one Bonus Action attack with them (if you used them during the Attack action). No other features that use a weapon can use Psychic Blades, because they literally don't exists outside of those two situations.
b) make them Light (makes sense IMO) in addition to being Finesse and Thrown. Have that replace their existing bonus action attack.
c) have their default Mastery be either Nick or Vex (so they still get only 2 of these attacks, without multiclassing ... while Nick would free up their Bonus Action, and Vex would mean they could move AND have advantage)
Thinking ahead, since we probably won't get an official update to the soulknife for years - would you give a soulknife's psychic blades weapon properties? Something like Vex seems obvious. In 5.14, soulknives are pretty competitive despite their PB damage not scaling (but would scaling add that much?). However, with weapon mastery, the PB could get relegated to a backup weapon, as a shortsword/dagger combo could prove more useful, especially once characters start picking up magic weapons.
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Nick would be great - allowing Soulknives to use Cunning Action, Psychic Teleportation, or Steady Aim without losing any attacks.
The easiest way would be for your Psychic Blades to have the mechanical stats of a shortsword (MH) and dagger (OH).
I might give them Vex, I probably wouldn't give them Nick since they already get a bonus to their off-hand attack.
I would:
a) make their blades appear any time they need to use them (examples: Defensive Duelist parry, if they have the Extra Attack feature via multiclass, etc.). Currently, you get 1 Attack action attack with them (no matter how many attacks you get via Attack action; because it appears when you start the Attack action, and disappears as soon as you use it), and one Bonus Action attack with them (if you used them during the Attack action). No other features that use a weapon can use Psychic Blades, because they literally don't exists outside of those two situations.
b) make them Light (makes sense IMO) in addition to being Finesse and Thrown. Have that replace their existing bonus action attack.
c) have their default Mastery be either Nick or Vex (so they still get only 2 of these attacks, without multiclassing ... while Nick would free up their Bonus Action, and Vex would mean they could move AND have advantage)