His Zerth blade transformed based on level and morale, so an accurate 3E conversion is a little more work than it first appears. For the record, here are it's stats from the game (cut & paste from Dan Simpson's "Planescape Torment Walkthrough") --

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1st stage (Dak'kon must have a minimum fighter level of 4):

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Morale: Less than 6 - Kinstealer (1)
6-14 - Chained Blade (1)
15 or above - Streaming Blade (1)

Weapon stats:

- Kinstealer (1)
Damage: 3-10 slashing
AC: +1
Enchantment: +1
Special: None

- Chained Blade (1)
Damage: 2-9 slashing
AC: +1
Enchantment: +1
Special: +2

- Streaming Blade (1)
Damage: 2-9 slashing
AC: +1
Enchantment: +1
Special: +2

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2nd stage (Dak'kon must have a minimum fighter level of 7):

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Morale: Less than 6 - Kinstealer (2)
6-14 - Chained Blade (2)
15 or above - Streaming Blade (2)

Weapon stats:

- Kinstealer (2)
Damage: 4-16 slashing
AC: +1
Enchantment: +2
Special: +2

- Chained Blade (2)
Damage: 4-12 slashing
AC: +4
Enchantment: +2
Special: +2, can memorise 1 additional second level spell

- Streaming Blade (2)
Damage: 4-12 slashing
AC: +2
Enchantment: +2
Special: +2, can memorise 1 additional second level spell

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3rd stage (Dak'kon must have a minimum fighter level of 10):

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Morale: Less than 6 - Kinstealer (3)
6-14 - Chained Blade (3)
15 or above - Streaming Blade (3)

Weapon stats:

- Kinstealer (3)
Damage: 6-24 slashing
AC: +2
Enchantment: +3
Special: +2

- Chained Blade (3)
Damage: 4-20 slashing
AC: +6
Enchantment: +3
Special: +2, can memorise 1 additional second level and 1 additional third
level spell

- Streaming Blade (3)
Damage: 4-20 slashing
AC: +3
Enchantment: +3
Special: +2, can memorise 1 additional second level and 1 additional third
level spell

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