Double strike, haste
Whenever this creature attacks, you get EE (two energy counters), then you may pay eight E. If you pay, untap all creatures you control, and after this phase, there is an additional combat phase.
Terror of the Peaksfinisher$28.06A red five-mana finisher that rewards attacking or landing on the battlefield with immediate game pressure. Like Lightning Runner, it turns a proactive threat into a source of explosive damage output.
Hellkite Chargerfinisher$4.55A hasty red threat that can generate extra combat steps, closely matching Lightning Runner's extra-combat game plan. It is more mana-intensive to activate, but fills the same combat-extension role.
Karlach, Fury of Avernusfinisher$22.61A red aggressive creature that directly grants an additional combat phase when it attacks. It is one of the closest functional analogues to Lightning Runner’s combat-doubling pressure.
Combat Celebrantfinisher$0.70A combat-focused creature that can exert to untap your team and create another combat phase. It performs a very similar attack-triggered extra-combat role, though with a different setup cost.
Aurelia, the Warleaderfinisher$18.88A classic extra-combat threat that rewards attacking by giving another combat phase. It plays the same broad role as Lightning Runner, though in Boros rather than mono-red.
Port Razerfinisher$0.92An aggressive creature that can chain multiple combat phases if it connects with combat damage. It is similar in function as a red extra-combat enabler, though it depends on combat damage rather than attack alone.
Aggravated Assaultfinisher$24.78A red repeatable extra-combat engine that mirrors Lightning Runner’s payoff of additional combat steps. It is a noncreature version of the same aggressive combo/finisher plan.
Relentless Assaultfinisher$2.48A direct extra-combat spell that can immediately extend a lethal board. It is the simplest budget alternative to Lightning Runner’s combat-duplication payoff.