Every URF game there is at least one Annie, Cassiopeia, or Brand.

{quoted}

cass and brand are free, and annie is 450 ip so practically everyone owns her. There are 10 chances for them to pop up.

You have 3 people with different types of shirts in drawers. Person 1 has a blue shirt, a pink shirt, and an orange shirt. person 2 has a green shirt, a white shirt, a purple shirt, and a black shirt. person 3 has a yellow shirt, and a grey shirt.

Now I put a red shirt into all 3 of their drawers. If I asked each person to pick a shirt at random without looking in the drawer, red has a higher chance to be pulled than any other color. Person 3 will have a higher chance of pulling the red shirt than person 2, but the chance of pulling it is still there for everyone.

Just increase the number of shirts and change it to champions, and make it 10 people instead of 3.

I thought URF makes use of all champs, not just what we have unlocked.