Venser, Corpse Puppet + Tainted Observer + Krark-Clan Ironworks

Venser, Corpse Puppet

Tainted Observer

Krark-Clan Ironworks

How it works

1. Cause a creature to enter the battlefield under your control.
2. Tainted Observer triggers, causing you to pay 2 to proliferate.
3. Venser triggers, creating a legendary 3/3 The Hollow Sentinel artifact creature token.
4. The Hollow Sentinel enters the battlefield, triggering Tainted Observer.
5. Holding priority, activate Krark-Clan Ironworks by sacrifcing The Hollow Sentinel, adding CC.
6. Resolve the Tainted Observer trigger, causing you to pay 2 to proliferate.
7. Repeat from step 3.