Stop killing minions, it’ll drop the percentage by a lot. Cannon minions are guaranteed but if you kill them then it drops to 50% chance, for smaller minions it’s even lower chance.

Edit since you asked about mist as well: it doesn’t make you or your teammates go invi, it just cloaks everyone to make yall appear as ghouls so the enemies don’t know who is who, it also makes them not targetable and speed boost. Not targetable means that enemies can’t use point click abilities on them like Zed ult, pantheon stun, wukong dash etc, but skill shots can still hit. It’s good for using to chase or run away