Who is Ivan from The Mote in God's Eye and what is their importance?

Ivan is a Motie Master who is sent to New Scotland with MacArthur as an ambassador. Although Ivan is a Master, he is not a Master to either Jock or Charlie, who are also sent with him. Ivan has been subjected to extensive hormone therapy to lock him into his male form. This will shorten his lifespan. If the Mediators were to die, Ivan would have no way to communicate with humans; that is outside his capability or skill set.