Priscilla, the Spider Queen
An unreleased champion that was left in development stage, her art assets remained in the game files.
It used to be rumored Priscilla had been reworked into Nidalee (she shared names with the Bestial Huntress at the time coupled with Nidalee's abilities applying poison and Prowl granting her stealth during production) but Steven 'Coronach' DeRose debunked it all on 22-May-2010. 
With Dominion's launch in September 2011 came the item (but was removed shortly after) which might have been referencing her since it increased point capture rate (and spiders use their webs to capture their meals)
The Shadow Isles Beckon
By NeeksNaman 
Swear your allegiance to the Shadow Isles, summoners! Shrouded in mist and shadows, this mysterious land promises death for those brazen or unfortunate enough to make their way to its shores. Most who journey here never return, but a few are embraced by this strange place and seize unimaginable power. Among these terrifying forces is Elise, the Spider Queen.
Elise, the Spider Queen Revealed
By NeeksNaman 
This patch, we'll welcome a champion with a lot of history into the League of Legends lineup: Elise, the Spider Queen. Originally concepted over three years ago, Elise proved to be a challenging champion to fully realize. Finally coming together as a transform champion, Elise has the ability to assume the form of either a regal mage or a deadly spider assassin.
- Abilities (Human Form)
Elise fires a skillshot that stuns the first enemy struck.
- Spider Form
Elise transforms into a menacing spider with new abilities. While in Spider Form, Elise deals bonus magic damage on attack and has increased Movement Speed, Armor, and Magic Resistance. Each level of her ultimate allows Elise to summon an additional spiderling.
- Abilities (Spider Form)
- Spider Queen
Elise summons her spiderlings to fight by her side. Spiderlings deal physical damage and take reduced damage from multi-target abilities.
- Venomous Bite
Elise lunges forward and bites her target, slowing them and dealing bonus damage based on how low its Health is.
- Skittering Frenzy
Elise and her spiderlings gain Attack Speed and heal her on each attack.
- On enemy cast: Elise and her spiderlings ascend high into the air and descend upon an enemy target.
- On ground cast: Elise and her spiderlings ascend high into the air, becoming untargetable for two seconds. Casting Rappel on a nearby enemy during this time will descend upon your target.
- Human Form
Elise transforms into a human form with new abilities. Each level of her ultimate allows Elise to summon an additional spiderling.
Like all transform champions, successfully playing Elise involves balancing two distinct kits. More than any of her counterparts, however, the Spider Queen's two forms embody distinct, but complimentary roles. Unlike Jayce, whose kit emphasizes flowing smoothly between ranged and melee skillsets, or Nidalee, who uses her cougar mobility to split push and create distance for her long ranged attacks, Elise's two ability sets separate definitively into mage and assassin roles.
In her human mage form, Elise specializes in keeping her distance using low-cooldown nukes and crowd control abilities. Her spells emphasize wearing down high-health targets in preparation for a brutal finish in spider form. At the heart of this gameplay is Neurotoxin which deals damage based on the opponent's current health. While in this form, she also generates a spiderling each time she casts a spell. Upon transformation into a spider, she summons these spiderlings to fight alongside her. Investing the time to build up your minion count is essential to performing a perfect assassination.
Once she's switched to her spider assassin form, Elise's kit takes on an entirely different theme. She gains a number of bonuses to her melee capabilities, and her spiderlings become active to help rapidly damage an opponent. Using Rappel, she can ascend above the battlefield, vanishing from sight and becoming untargetable for a short duration. Once she's suspended, she can lower herself upon a nearby target, surrounding them with spiderlings. Boosting her minions' Attack Speed with Skittering Frenzy can quickly burst down a surrounded enemy, leaving them vulnerable to execution with Venomous Bite.
Using both spider and human form effectively is the key to making the most out of the Spider Queen. Having the good judgment to stay safe in your mage form while you fight to create the opportunity for a clean spider kill will make or break your success on the Fields of Justice.
Inside Design: Weaving the Spider Queen's Web
By ByronicHero 
Elise, the Spider Queen, is poised and ready to unleash her horrific powers on the Fields of Justice. We spoke to some of the Rioters involved in bringing Elise to life and asked them about the challenges of arachnophobia, visual design, sound design, and what's so damn cool about transforming into a monstrous, man-eating spider. Here's the inside scoop on Elise from the developers behind this dangerous new champion.