Indestructible things are very relative... Flattering a changeling have lots of strage things, included in that changeling dying when idestructible if sycophant dies. I dont know if thats how it is worked, but looks very strange the relactions of master-servile when changeling traded and they become opposing units. Maybe if control of master is lost, they both could die too... or it is a unilateral codependance? I'm still not sure but i think idestructible templars die if its servile dies.