In simple words, it can be stated that the Bad Omen status effect causes a raid to appear when the player affected by it visits a village. As previously said, it occurs after you kill a raid captain (the one with the banner), which you may usually come across at pillager outposts, p...
and yet also wake me up at midnight to tell me all about their nightmare that somehow divulges into an hour long monologue about why Roblox is, like, really awesome.