1v4 Baron hunt game mode concept.

4 champions vs. Baron.

Summoner's Rift, but no lanes, blocked off by debris caused by Baron. Turn the lanes into added jungle space, and add in more camps.

Game starts. There are several viable options. The players can attempt to farm the jungle and outscale Baron, or hunt him down asap. Baron also has several options. Farm up to late game, or fight early.

As experience would be split among teammates, you could split up for more XP gain, but this would be a huge risk factor, as Baron could try to steal camps, which would turn any 1-2 champs farming without the group into easy gold + XP for Baron.

That's the basic idea + meta that I can think of off the top of my head. The way I see it, it could be balanced so Baron would naturally scale harder than 4 champions grouped and farming the whole time, but be outscaled by a split, farming team, while he'd have more opportunities to catch them out.

For the Baron gameplay, I was thinking he'd have a tunneling mechanic (I've procrastinated, the original idea was before Rek'Sai and with old Baron model.) He couldn't move while surfaced. He would be able to leave mini baron heads behind, that surface and act as visible wards until killed. He could have an ability that causes a catastrophic rupture to block movement, so he could try to force fights by creating a (similar to Anivia) wall and making the enemy team have to run away around him. He could re-tunnel if the fight isn't going in his favor, but he would suffer from a bad fight more than the champions, as an injured ADC can still help a tank kill buffs, but injured Baron runs the risk of dying to camps or having the enemy team split and hunt him down.

The game mode would also work with Ebonmaw or Dragon. Even a few champions, although the only way I can see that it would be fair and fun would be a melee champion with ranged attacks, which narrows it down. I could see an extra large Cho'Gath 4v1, or a Villain Rumble with an extra large suit.

If you have any sweet ideas to throw into the mix, I'd love to hear them. I've had this idea bouncing around in my head for 3 years now and I'm too disorganized to get it down on paper in a way that makes it look enticing.