Major changes:

Removed the eyes
Removed two lungs
Added two spiracles
Created the entity file
Added the hierarchy (which has been tested and is functional, besides lacking a broker)
Scythod playable in DF mode (implied by the last line) (remove the CIV_CONTROLLABLE tag to disable it)
Scythes aren't severed at first tap
Stompstabbing with legs does piercing damage instead of blunt damage (changed the material)
Added the language (Boatmurdered is "Pridacissa", Spearbreakers is "Alycacsif")

Little bit of the language:
_{[T_WORD:LITTLE:abonna]
[T_WORD:EARLY:kapkok]
[T_WORD:LATE:bil]
[T_WORD:LIFE:p'k]
[T_WORD:CHEESE:chh'k]
[T_WORD:FIGURE_OBJECT:ta'c'thcyl]
[T_WORD:HOPE:hatsa]
[T_WORD:BODY:afyd]
[T_WORD:WALK:ata'l]
[T_WORD:HOUR:ta'la]
[T_WORD:SIT:arad]
[T_WORD:MOMENT:bitisk]
[T_WORD:BEAUTY:adara]
[T_WORD:JUDGE:sca'lk]
[T_WORD:WISH:k'k]
[T_WORD:RESPECT:chycsoktac]
[T_WORD:MARK:annit]
[T_WORD:HEAVY:af'lc]
[T_WORD:TRIAL:chocsca]
[T_WORD:PRACTICE:athc'ra'tsa]}
As you can see... very alien, though not unpronounceable, if you don't mind making click sounds instead of using vowels.