Substitute Sweeper (NGas)

With a Timid nature, Eternamax can avoid OHKO hits from slower foes, including most opposing Eternamax. Night Shade, Taunt, and Horn Drill together cannot be walled long-term without Cramorant-Gorging and a Ghost-type with recovery. The combination of Trick, Rapid Spin and Fissure over Taunt, Night Shade and Horn Drill is slightly less risky against opposing Cramorant-Gorging, but is weaker into foes behind Substitute.

Switch Eternamax in when a slower opponent is unlikely to use an OHKO move, for example when an opposing Giratina is at low enough HP to strongly consider using recovery. Keep Substitute up when possible, disable recovery and gain Black Sludge recovery turns via Taunt, and chip and KO foes with Night Shade and Horn Drill.

Cramorant-Gorging can inhibit Eternamax's ability to make progress by increasing the range of Pokemon that can use recovery moves before Taunt. Encore from faster foes, like Regieleki and Calyrex-Shadow, can force Eternamax out if it is locked into Substitute.