Ha, I spent way too long figuring this out, Hugo already got you an answer, but this is my own solution, it might be a little more true to the game.
Ready to be dropped into its own file and slapped onto a humanoid.
body_necromorph
[OBJECT:BODY]
[BODY:HUMANOID_NECROMORPH]
[BP:UB:upper body:upper bodies][UPPERBODY][CATEGORY:BODY_UPPER]
[DEFAULT_RELSIZE:1000]
[BP:LB:lower body:lower bodies][CON:UB][LOWERBODY][CATEGORY:BODY_LOWER]
[DEFAULT_RELSIZE:1000]
[BP:HD:head:STP][CON:UB][CATEGORY:HEAD]
[DEFAULT_RELSIZE:300]
[BP:RLA1:right blade:STP][CON:RUA1][LIMB][THOUGHT][RIGHT][CATEGORY:ARM_LOWER]
[DEFAULT_RELSIZE:500]
[BP:LLA1:left blade:STP][CON:LUA1][LIMB][LEFT][THOUGHT][CATEGORY:ARM_LOWER]
[DEFAULT_RELSIZE:500]
[BP:RUA1:first right lower arm:STP][CON:UB][LIMB][RIGHT][CATEGORY:ARM_UPPER]
[DEFAULT_RELSIZE:200]
[BP:LUA1:first left lower arm:STP][CON:UB][LIMB][LEFT][CATEGORY:ARM_UPPER]
[DEFAULT_RELSIZE:200]
[BP:RUA2:second right upper arm:STP][CON:UB][LIMB][RIGHT][CATEGORY:ARM_UPPER]
[DEFAULT_RELSIZE:200]
[BP:LUA2:second left upper arm:STP][CON:UB][LIMB][LEFT][CATEGORY:ARM_UPPER]
[DEFAULT_RELSIZE:200]
[BP:RLA2:second right lower arm:STP][CON:RUA2][LIMB][RIGHT][CATEGORY:ARM_LOWER]
[DEFAULT_RELSIZE:200]
[BP:LLA2:second left lower arm:STP][CON:LUA2][LIMB][LEFT][CATEGORY:ARM_LOWER]
[DEFAULT_RELSIZE:200]
[BP:RH2:second right hand:STP][CON:RLA2][GRASP][RIGHT][CATEGORY:HAND]
[DEFAULT_RELSIZE:80]
[BP:LH2:second left hand:STP][CON:LLA2][GRASP][LEFT][CATEGORY:HAND]
[DEFAULT_RELSIZE:80]
[BP:RUL:right upper leg:STP][CON:LB][LIMB][RIGHT][CATEGORY:LEG_UPPER]
[DEFAULT_RELSIZE:500]
[BP:LUL:left upper leg:STP][CON:LB][LIMB][LEFT][CATEGORY:LEG_UPPER]
[DEFAULT_RELSIZE:500]
[BP:RLL:right lower leg:STP][CON:RUL][LIMB][RIGHT][CATEGORY:LEG_LOWER]
[DEFAULT_RELSIZE:400]
[BP:LLL:left lower leg:STP][CON:LUL][LIMB][LEFT][CATEGORY:LEG_LOWER]
[DEFAULT_RELSIZE:400]
[BP:RF:right foot:right feet][CON:RLL][STANCE][RIGHT][CATEGORY:FOOT]
[DEFAULT_RELSIZE:120]
[BP:LF:left foot:left feet][CON:LLL][STANCE][LEFT][CATEGORY:FOOT]
[DEFAULT_RELSIZE:120]
I applied it to a human copy, and it worked.
Pretty much replace :HUMANOID: with :HUMANOID_NECROMORPH:
It falls over when you slice off one blade, and it dies if you chop off both.
If I added [NO_PAIN] in the creature, it would probably not fall over if it loses a blade.
It apparently needs [EXTRAVISION] and [NO_BREATHE] or it dies fast and can't find you.
I have no idea how to make the blades sharp, so you'll have to ask someone else for that.