The second ranked Runebound skill Erik got through his thundersnow affinity was weapon enhancement. By channeling his affinity through his weapon, he could both electrocute and freeze his opponent on every hit.
In this case, he intended to slow and hinder Liv until he could trap her.
But that would take a little more effort.
A ghoul didn't feel any pain. It's muscles could get tired and might strain under the constant application of cold lightning and ice patches, but it would take quite a while.
On the other hand, a regular Runebound or Arcanist could use their energy to easily break up the ice and negate the rampaging lightning. Against opponents like that, this ability would merely be an annoyance, while sapping some of their energy. It would mainly be useful in fights of endurance.
But a ghoul couldn't use that energy at all. All they had was their body. Slowly, the ice would accumulate, and the after effects of lightning would wreak havoc.