Halo Fountain, Incubation Druid, and Karn, the Great Creator

Prerequisites

• Halo Fountain on the battlefield
• Incubation Druid on the battlefield
• Karn, the Great Creator on the battlefield
• Halo Fountain and Incubation Druid do not have summoning sickness
• Incubation Druid has at least one +1/+1 counter on it

Steps

1. Activate Karn's first loyalty ability by putting a loyalty counter on it, causing Halo Fountain to become an artifact creature until end of turn
2. Activate Incubation Druid's first ability by tapping it, adding
3. Activate Halo Fountain's second ability by paying , tapping it and untapping it and Incubation Druid, causing you to draw a card
4. Repeat from step 2

Results

• Infinite card draw
• Infinite draw triggers
• Near-infinite colored mana
• Near-infinite creature tokens
• Near-infinite untap of creatures you control
• Near-infinite mana creatures you control can produce