Android 21 who used to be a scientist named Vomi, turned into an android by Dr.Gero is very cunning and evil. Her plan is world domination alongside her offsprings but as an android it is impossible for her to concieve and because the dragon balls are gone. She can't exactly ask shenron either. Android 21 is very cunning and plo and a very capable scientist. She can fix any problem if given enough time to troubleshoot it, she needed a a prime specimen for her plan.