I was wondering about this as well. It sounds similar to what Eshonai did to change forms, only in her case the spren appears to connect to Odium. And he then proceeds to control her in a very similar way that Ruin controls the Inquisitors. Maybe there's a correlation to these spheres and hemalurgic spikes. Like maybe they operate in the same way in establishing connection with shards, but the mechanics of making them work are different. Has anyone asked Mr. Sanderson about this yet?
Maybe the Eyre have been to Roshar and studied the spheres and gemstones, and the Parshendi's transforming method. Then made their own versions(and I'm am 98% sure that's what Kelsier found, andstole). They did seem to know about other worlds, like Threnody, after all.