Elise

Strengths

Spider Form is most effective at finishing off enemies with low health; Human Form's Neurotoxin does more damage to healthy foes.
When in Spider Form, Spiderlings will attack the target that Elise uses Venomous Bite on.
Elise's Spider Form and Spider Form abilities do not cost mana and can be prioritized when you are trying to conserve mana.

Passive · Spider Queen — Human Form: When Elise's abilities hit an enemy, she gains a dormant Spiderling. Spider Form: Basic attacks deal bonus magic damage and restore health to Elise.
Q · Neurotoxin / Venomous Bite — Human Form: Deals damage based upon how high the target's Health is. Spider Form: Lunges at an enemy and deals damage based upon how low their Health is.
W · Volatile Spiderling / Skittering Frenzy — Human Form: Releases a venom-gorged Spiderling that explodes when it nears a target. Spider Form: Elise and her Spiderlings gain Attack Speed.
E · Cocoon / Rappel — Human Form: Stuns the first enemy unit hit and reveals them if they are not stealthed. Spider Form: Elise and her Spiderlings ascend into the air and then descend upon target enemy. After descending on an enemy target, Elise's bonus damage and healing from Spider Queen is increased.
Ultimate · Spider Form — Transforms into a menacing spider, reducing her attack range in exchange for Move Speed, new abilities, and a Spiderling swarm that will attack her foes.

A suggested 5-lane lineup built around Elise, based on hero partnerships and role synergy — not win rate.