Game Mode: PENTAKILL (you probably haven't heard this one before, though)
Alright, let's throw basically everything League is out the window. We're combining DDR with League and a bit of bullet hell. I figure League is already pushing the label already with Poro King and Ascension...
SO. This map is on the Howling Abyss. Everyone is given one of Sona, Mordekaiser, Yorrick, Karthus, or Olaf. You can trade in lobby. Always the Pentakill skin, even if you don't have it. Music from the Smite and Ignite album plays at all times.
Champions' basic attacks are removed. Q W E and R abilities are removed, and your passive and summoner abilities are modified. A randomly generated, but same for everyone DDR style "beatmap" is generated, except instead of the arrow keys, its the Q, W, E, and R buttons. You generate mana and health based off of your health regen by pressing Q, W, E, or R when the beatmap lines up and how closely you hit the note, but do not gain health otherwise. As you hit notes, the cooldowns on your summoner abilities decrease, but they do not decrease normally.
Q: When you successfully hit a Q note, you fire a slow moving projectile towards the cursor that travels a long distance, locked to an axis parallel to the game map. Basically, a forwards or backwards shot. If you get a PERFECT, you fire two shots in succession. This scales off of AD, and deals bonus damage to minions.
W: When you hit a W note, you fire two projectiles perpendicular to the bridge. These projectiles are wider, pierce through minions, but don't travel as far. This scales off of AD. On a perfect, they are both stronger and larger.
E: When you hit an E note, you create an AoE burst around you that deals bonus damage to minions. On a perfect, you also fire 4 Q-style shots on all four diagonal directions. This scales off of AD.
R: When you hit an R note, you gain a brief movement speed boost that lasts one beat. On a PERFECT, it lasts two beats.
As you hit these notes, you build up a combo meter that caps out after a certain point. The combo meter grants bonus AD and AP until you screw up.
Each champion gets a new passive, and two summoner abilities. This is just an example:
SONA -- The Support
Passive: Glower Chord Sona grants health regeneration over time to all nearby allies, scaling off her AP and Combo Meter
D: Sanguine Spray Sona fires a projectile towards her cursor that damages enemies and heals allies that it passes through. The heal and damage scales off of AP.
F: Decrescendo Sona calls global projectiles from her nexus (they travel at around the same speed as Ashe's ult). Enemies hit are stunned and forced to dance. It also deals damage scaling off of AP.