The final big proliferate-friendly card I'd recommend is Tezzeret the Seeker, which can find your important artifacts more efficiently than the other tutors can, plus it also acts as huge ramp if you've got an Everflowing Chalice or Empowered Autogenerator on the battlefield
Latest decks CAS 3 / 0 CAS 1 / 0 CAS 0 / 0 CAS 3 / 6 MDN 6 / 0 CAS 0 / 0 CAS 45 / 53 CAS 2 / 6 CAS 1 / 0 CAS 8 / 5 MDN 3 / 18 CAS 0 / 0 CAS 0 / 0 PLN 70 / 19 CAS 1 / 2 CAS 2 / 2 CAS 6 / 1 CAS 0 / 0 CAS 2 / 0 EDH 0 / 7 MDN 0 / 1 CAS 5 / 1 CAS 16 / 6
The versatility of counterspells gives blue players reassurance they wont get blown out in the long game, and the ability to steal an opponents best card is the ultimate haymaker during back-and-forth midrange battles
It even mills cards itself to grow, though I wouldnt recommend relying on it as your only source of mill
It gets better in EDH since youll drain all opponents at once
This includes many zero mana artifacts such as Jeweled Lotus and Lotus Petal, as well as spells with free alternate costs such as Deflecting Swat and Fierce Guardianship, since they do not require mana to cast when the criterion to cast them for free is met