If you have cards in your deck that boost other units, you can temporary remove Saesenthessis' immunity and stack a bunch of boosts on her. The immunity will return after your turn ends, so that's a good way to stack points and protect them.
As for Nilfgaardian Knight, it synergizes well with cards that drain boosts or switch power with an enemy like Regis and Master of Disguise. I once made a fun deck that focused on buffing the enemy, it had Wyvern Scale Shield, Rainfarn, Nilfgaardian Knights and stuff like that. I would buff the enemy like crazy and if he buffed himself too, all the better, and at the end of the round I would use Regis or Master of Disguise to take all my points back.