Sometimes the universe just doesn't operate the way it should. That's what wizards are for. If two species can't get along, or the timeline's not flowing straight, or your star just needs a little maintenance, a friendly local wizard should show up with an intervention soon.
Being a wizard is a big responsibility. Not everyone is cut out for it, so the Powers That Be choose their wizards very carefully. And before each wizard takes up their power, before they embark on the Ordeal that launches their career, every wizard swears one recension or another of the Wizard's Oath. It's part mission statement, part pledge of allegiance, and it's one of the most important declarations they will ever make, because the war against entropy is not for the faint of heart.