If I was to cast pox or death cloud with It That Betrays on the field and I sacrificed It That Betrays to pox during the sacrifice creatures step do I gain control of each of the creatures my opponents sacrificed? I know I would miss out on the lands because pox's effects happen separately and It That Betrays wouldn't be on the battlefield as lands are sacrificed but does It That Betrays "see" other creatures die as it dies and give them to me? Thank you very much for your answer!
Pox
It That Betrays
Yes. Anything sacrificed at the same time as It that Betrays will trigger It that Betrays. You will get whatever creatures they sacrificed.