Thopter Squadron + Crystalline Crawler + Yotian Dissident + Roaming Throne

Thopter Squadron

Crystalline Crawler

Yotian Dissident

Roaming Throne

How it works

1. Activate Thopter Squadron's first ability by paying 1 and removing a +1/+1 counter from it, creating a 1/1 Thopter artifact creature token.
2. When the Thopter enters, Yotian Dissident triggers twice due to Roaming Throne, putting a +1/+1 counter on Thopter Squadron and Crystalline Crawler.
3. Activate Crystalline Crawler by removing a +1/+1 counter from it, adding 1.
4. Repeat.