Hi there,
Tahm Kench's Devour ability has a bit of an annoying interaction with Olaf when he's using his ultimate. If TK tries to Devour Olaf during Ragnarok, it plays the animation and sound but doesn't work or go on cooldown. It's really distracting and feels like a bug, because if an ability is used on an invalid target it shouldn't run anything associated with it.
Olaf is not an invalid target in this case, and it is not a bug. The way it is coded, the animation and sound are associated with pressing the spell in range of a valid target. Though Olaf is invulnerable to cc during his ultimate, he is still a target which you can use devour on. His ultimate does not disable the ability to use cc spells on him, it simply negates the effects of any cc debuffs which are placed on him. In your case, you try to eat him, but the spell does not take effect because the action of eating him is a cc effect he is invulnerable to. As for why it is not putting your W on cooldown, I am unsure, because it certainly should since you used it.
NOW, DEVOUR DOES NOT WORK ON OLAF AND THE SPELL IS COOLING DOWN WHEN YOU USE IT ON HIM WHILE RAGNAROK IS ACTIVE !!!
