Goblin Welder, and Sewer-veillance Cam

Prerequisites

• Goblin Welder on the battlefield
• Sewer-veillance Cam on the battlefield

Steps

1. Activate Goblin Welder by tapping it, causing you to sacrifice Sewer-veillance Cam and return another artifact from your graveyard to the battlefield
2. Sewer-veillance Cam triggers, untapping Goblin Welder
3. Activate Goblin Welder by tapping it, causing you to sacrifice the artifact returned in step 1 and return Sewer-veillance Cam from your graveyard to the battlefield
4. When Sewer-veillance Cam enters, it triggers, untapping Goblin Welder
5. Repeat

Results

• Infinite ETB
• Infinite LTB
• Infinite death triggers
• Infinite recursion of artifact creatures you control
• Infinite sacrifice triggers