Thranduil, the Elvenking, Devoted Druid, and Tromell, Seymour's Butler

Prerequisites

• Thranduil, the Elvenking on the battlefield
• Devoted Druid in the graveyard
• Tromell, Seymour's Butler in the graveyard

Steps

1. Activate Thranduil using Tromell's ability by tapping it, putting a +1/+1 counter on Thranduil for each nontoken creature that entered under your control this turn
2. Activate Thranduil using Devoted Druid's second ability by putting a -1/-1 counter on it, untapping it
3. Activate Thranduil using Devoted Druid's first ability by tapping it, adding
4. Activate Thranduil using Devoted Druid's second ability by putting a -1/-1 counter on it, untapping it
5. Repeat

Results

• Infinite +1/+1 counters on a creature
• Infinite green mana
• Infinite proliferate