Master Biomancer has at least one +1/+1 counter on it
Steps
Activate
Master Biomancer using
Grist's first loyalty ability by putting a loyalty counter on it, causing you to create a 1/1 Insect creature token and mill a card, and then put a loyalty counter on
Master Biomancer and repeat the process if the card was an Insect
The Insect enters the battlefield with at least three +1/+1 counters on it due to