Sliver Queen, Quickbeam, Upstart Ent, Devoted Druid, and Xenograft

Prerequisites

• Sliver Queen on the battlefield
• Quickbeam, Upstart Ent on the battlefield
• Devoted Druid on the battlefield
• Xenograft on the battlefield
• Devoted Druid does not have a -1/-1 counter on it and does not have summoning sickness
• "Treefolk" chosen with Xenograft

Steps

1. Activate Devoted Druid's first ability by tapping it, adding
2. Activate Devoted Druid's second ability by putting a -1/-1 counter on it, untapping it
3. Activate Devoted Druid's first ability by tapping it, adding
4. Activate Sliver Queen by paying , creating a 1/1 Sliver creature token
5. When the Sliver enters the battlefield as a Treefolk due to Xenograft, Quickbeam triggers, giving Devoted Druid and up to one other creature +2/+2 until end of turn
6. Activate Devoted Druid's second ability by putting a -1/-1 counter on it, untapping it
7. Repeat

Results

• Infinite creature tokens
• Infinite ETB
• Infinitely large creatures until end of turn except Devoted Druid