How the hell does a champion dash or tumble through a wall?

Usually they go over the wall, as if the wall used to climb or dash over is "climbable terrain." This of course doesn't apply to Flash, wherein the champion teleports and may reappear on the other side of the wall if they use it correctly.

ALSO: Its a game. If logic applied, the screen would be black every time you played , and tits would be falling out ALL THE TIME.

Let me get this straight: there's various monsters, creatures, magicians, vampires, werewolves, sentient robots, and little girls summoning giant flaming bears running around - and you're worried about how its possible to dash through walls?

we'd have to go over this ability by ability, anyways its a jungle so you can go through the wall if you know your way sort of like the thorny walls in pool of radiance ™

tumble? vayne? u got outplayed so hard. u were chasing the enemy vayne and didnt realize her skillset at all. she ulted and went invisible near a wall and u flashed over it thinking she tumbled there, when in fact she was just invisible near the wall. u got outplayed son!

tumble doesn't go through walls unless you're talking about J4's.

well, Leona can run through dead trees (New Dawn cinematic), so her E-ing over walls isn't that strange