Zaphael continued using his Voltaskill to direct the Beasts where he wanted them to go. Why was he directing all three riotrunners and not just the one they were riding upon? Well…he didn't want it to get lonely, that was all.
This one of his Skills required the least amount of Amassed Ether to Harness. He was simply Forging thin sparks of Volta—thin enough to not be noticed by untrained eyes—to communicate with the riotrunners where he wanted them to head to. He hadn't used it specifically on riotrunners before this, but by the looks of it, so far it was working just as well on them as on other Beasts.
Oh, he was also using another one of his Skills, that allowed him to appear less threatening to Etherbeasts like the one he was on and the two on either side of it.