What should riot do next for PvE?

i'm not going in on the RPG subject as the opinions are very mixed on that one.

anyways what do you think would be cool for riot to make into a PvE gamemode for an event (rip RGM rotation)?

i for example think they could expand their shadow isles lore and make you have to fight against the black mist and encounter boss champions on the way (think a huge spider fight with elise or a multiple fase karthus fight) and ending with maybe facing off against the ruined king in the 'onslaught' mode

would love to hear your ideas! [slayer-jinx-wink]