Author commentary: It's a pretty good trick Terezi pulls here. Manipulating an omniscient, omnipotent creep to maim a murderous, overpowered cheater. She used a few known facts to her advantage and set them both up perfectly. There are probably a couple lingering questions about this. For one thing, did Terezi know that Doc would make the cue ball blow up in Vriska's face after she told him? How did she know it could explode, or the fact that he would make it explode if he got pissed? The simplest explanation is that she just cleverly pried out all this information from Doc himself through some casual conversations. She knew Vriska had the object. She probably was able to get Doc to blab about his seeds without tipping the fact that Vriska had one, so she could use the info to her advantage later. He sure likes to run his invisible mouth, so it was probably easy. She learned he was very sensitive about his seeds, and he doesn't want anyone touching them. He must have conveyed he'd rather destroy them himself rather than let them fall into others' hands without his intent. (Rose he allowed, for instance, because it served his purpose.)