Extra deadly spikes can pop through 2 layers per spike.
Deadly Spikes is the fourth upgrade of Path 3 for the Spike Factory in BTD6. It allows all spikes of the Spike Factory to pop two layers instead of one layer, effectively doubling its power. It costs $2,975 on Easy, $3,500 on Medium, $3,780 on Hard, and $4,200 on Impoppable.
Deadly Spikes now attacks 4x as fast for the first 2.5s of a round.
All crosspaths for the BTD6 Deadly Spikes (left path 1, right path 2)