The mind control connection can also be used by the player. Once the player picks up on what is happening to him, he may be able to use the connection to glean information directly from the enemies’ mind or even controlling the lesser parts of a hivemind himself.
With newer players, this is especially fun to do with little notes that you hand to the inflicted player. Stuff like:
You feel like you know this creature before you. Its’ mind is franticly clawing at your awareness. You concentrate and feel your mind connecting to it. Maybe if you concentrate hard enough, you can order it to do your bidding. Roll a wisdom saving throw.
Afterwards, depending on his roll, give him a few notes with possible commands for that creature on it. If he starts abusing that power hand him another note reading something like:
As you order the creature to do your bidding, you feel the spark of a foreign intelligence on the edge of your awareness. Are you being watched from afar?
This is meant as warning – if he continues to overuse the neural network, begin spawning stronger creatures that are part of the hive mind / neural network. Always take the notes away after the player has read them. He can talk about it in character, but the other players will still be curious and wary if he’s telling the truth.