I imagine Peeves to be something between Puck and Io from Dota and these little Pixies from Harry Potter, I don't have an image so the traditional stats window is not needed, I hope.
When in combat, Peeves ignores unit collision and gains 5 / 7.5 / 10 / 12.5 / 15 movement speed every second, up to a cap of 25 / 37.5 / 50 / 62.5 / 75+10% AP movement speed.
Peeves also deals 10 + (2 × level) +20% AP magic damage to enemies he passes through. Enemies can only be damaged once a second.
Peeves sends wispy orblet that persists for 5 seconds to target location, dealing magic damage to enemies it passes through and to enemies who walk through it. Each following enemy takes 10% less damage and causes Orbletty to fade a bit. When damage counter goes to 0%, Orbletty completely disappears.
Damage to first target: 70 / 120 / 170 / 220 / 270 +80% AP
Swapify: Peeves can swap positions with Orbletties. After swapping, Orbletties explode, dealing magic damage in small area around them.
Explosion damage: 150 / 200 / 250 +70% AP
Orbletty is a pass-through linear skillshot that leaves an area of effect with the same effcts.
Spell shields damage will be blocked, but Orbletty will fade as if it dealt damage.
Orbletties grant vision in a small radius around them.
COST: 100 mana
Peeves links to target enemy or ally champion for up to three seconds, lowering target's movement speed if it's an enemy, or sharing his current innate movement speed bonus with ally target and any ally that crosses the beam. Enemies who cross the beam take magic damage.
Magic damage can only be applied once a second and is calculated separately from innate's pass-through damage.
COST: 80 mana
COOLDOWN: 15 / 13.5 / 12 / 10.5 / 9
Peeves pulls nearby enemies slightly towards him, slowing them for one second afterwards and receiving bonus movement speed for each enemy champion caught for three seconds and incoming damage reduction for one second.