Gilder Bairn + Elemental Mastery + Pentad Prism

Gilder Bairn

Elemental Mastery

Pentad Prism

How it works

1. Activate Elemental Mastery by tapping Gilder Bairn, producing its effect.
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 three 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.