The basics of his magic is that he can divide or multiply the weight of objects or creatures.
Objects are easy, people take effort to maintain.
What he usually does with the orbs is sling them on a rope in the direction he wants, then dramatically increases the weight of the orb just before it hits.
I described he wanted it to be heavy, but not heavy enough to break ribs (since he doesn't want himself or Galen using lethal magic). But that's still the force of a sledgehammer coming straight for him. Putting your unprotected finger in the way is a bad idea. hehe.