Gilder Bairn + Pentad Prism + Citanul Hierophants

Gilder Bairn

Pentad Prism

Citanul Hierophants

How it works

1. Activate Citanul Hierophants by tapping Gilder Bairn, adding one mana.
2. Activate Gilder Bairn by paying 2G/U and untapping it, doubling each counter on Pentad Prism.
3. Activate Pentad Prism as many times as necessary by removing counters from it, adding at least two mana.
4. Repeat from step 2.
5. Once you have infinite counters on Pentad Prism, you may instead double the counters on any other permanents.