Yavimaya, Cradle of Growth + Life and Limb + Plague Engineer

Prerequisites

• "Saproling" chosen with Plague Engineer.

Steps

1. 1Yavimaya causes all lands to be Forests in addition to their other types, thus Life and Limb causes all lands to be 1/1 Saproling creatures.
2. 2Because Plague Engineer gives all Saprolings your opponents control -1/-1, they die as a state-based action due to having zero toughness.
3. 3Whenever an opponent plays a land, it will also die as a state-based action.

Effects

• Destroy all lands opponents control
• Destroy all lands that enter the battlefield under an opponent's control
• Lock
• Mass Land Denial