Requires

Voltaic Construct must be on the battlefield. Gilded Lotus must be on the battlefield. Karn, Silver Golem must be on the battlefield. Gilded Lotus does not have summoning sickness. Mana needed:

Steps

1. Activate Karn by paying , causing Gilded Lotus to become an artifact creature until end of turn.
2. Activate Gilded Lotus by tapping it, adding three mana of any one color.
3. Activate Voltaic Construct by paying , untapping Gilded Lotus.
4. Repeat from step 2.

Results