Berta, Wise Extrapolator + Agatha's Soul Cauldron + Farmstead Gleaner + Mikaeus, the Lunarch

Berta, Wise Extrapolator

Agatha's Soul Cauldron

Farmstead Gleaner

Mikaeus, the Lunarch

How it works

1. Activate Berta using Mikaeus's first activated ability by tapping them, putting a +1/+1 counter on Berta.
2. Berta's second ability triggers, adding one mana of any color.
3. Activate Berta using Farmstead Gleaner's ability by paying 2 and untapping them, putting a +1/+1 counter on Berta.
4. Berta's second ability triggers, adding one mana of any color.
5. Repeat any number of times.
6. Once you have infinite +1/+1 counters on Berta, you may repeat the loop using Mikaeus's last activated ability in step 1 instead, putting infinite +1/+1 counters onto creatures you control.