Leikar knew zombies and knew how to fight them.
Most important thing was to keep them from getting too close to spread their contagion.
His fire spells did just that, and this kind of undead followed orders absolutely. They would continue charging headlong into the flames unless their master commanded them otherwise.
When no command came, Leikar assumed the Knight had already killed the necromancer.
They’d won, but he still wondered if he’d given up his own life helping the man.