Berta, Wise Extrapolator + Assassin Den + Biomancer's Familiar + Training Grounds

Berta, Wise Extrapolator

Assassin Den

Biomancer's Familiar

Training Grounds

How it works

1. Activate Assassin Den by paying due to Training Grounds and Biomancer's Familiar, putting a +1/+1 counter on Berta.
2. Berta triggers, adding .
3. Repeat.

This intricate loop relies on Assassin Den's activated ability, whose cost is deeply discounted from {3}{U} down to just {U} thanks to the stacked cost-reducers Training Grounds and Biomancer's Familiar. By targeting Berta, Wise Extrapolator with this cheap ability, you place a +1/+1 counter on Berta, which in turn triggers Berta's mana-generation ability to float a blue mana. That generated mana can immediately pay for the next activation of Assassin Den, allowing you to feed the loop infinitely and grow any chosen creature to colossal proportions.