Arms are a good idea , but 4 - 6 arms sounds too much like a marilith ... it'll have 2 arms.
It'll have these ability scores : Str 15, Dex 10, Con 17, Int 13, Wis 15, Cha 11.
So, here are its attacks :
Attacks : Spear + 11 melee, sting +6 melee; or beam +11 ranged touch
Damage : Spear 1d8+2; sting 1d8+1 plus poison; beam 1d4 plus stunning
Please suggest possible special abilities. It will have stunning (Fort or be stunned 1d2 rounds) on a beam hit, and poison (primary damage paralysis 1 minute, secondary damage paralysis 1d4 turns) on a sting attack hit. Any other ideas? Maybe something related to force, since its beam is a "laser" ray of pure force.