Changeling by Aslo

Stats

Low health but high regen
No mana
1 attack per second
attack damage is depended on how much damage he receives.
Melee range

Level 1
Corruption: deal 100 damage and give the target 25% vulnerability.
15 second cooldown
Caustic Spray: channel to 5% slow the target, increases by 5% every 1.5 seconds to a max of 30%. deals 2 damage per second for every % of slow.
10 second cooldown.
Consume: deal 5% max health damage and reduce your cooldowns by 5 seconds.
15 second cooldown.

Level 4
For the swarm: Mercenaries and minions deal 75% less damage to the changeling and nearby minions deal 150% damage. (no visual indicator for the enemy team.)
Primal: Increases the duration of the changeling form buff by 75%
Stronger Carapace: increases the effectiveness of unstable presence block to 50%
Rapid Regeneration: doubles your health regen when out of combat for 5 seconds

Level 7
Detection: when using overseer drop the area will be revealed.
Noxious: has an aoe effect around him that deals 70 damage per second. can be toggled.
Mend restore 20%$ of your max health instantly and 15% of your max health over 5 seconds. the healing over time is also of nearby allies.
Blinding clouds: Contaminate also blinds hero's

Level 10
Ultimate Shapeshift: No longer gives the allied hero vulnerability and makes him invincible for 3 seconds and yourself for 1.
Infiltrator: you are now able to shapeshift as an enemy hero which makes both of you target able by enemy spells. using shapeshift on an enemy hero gives this ability a 30 second cooldown.

Level 13
Saboteur: Regen Globe Trap cooldown reduced by 10 seconds and regen globes now reduce the cooldown by 10
Pneumatized Carapace: reduce the cooldown of overseer drop by 10 seconds and reduce the time it takes for the overseer to arrive by 5 seconds.
Metabolic boost: change the changeling speed to 30%
Monarch blades: basic attacks cleave for 80% damage.

Level 16
Surprise attack: When you attack while shapeshifted as a minion you will deal 200% basic attack damage.
Hardened shell: when you use overseer drop your will gain 100% of your maximum health as shields for 5 seconds.
Blood for blood

Level 20
Regenerative acid: Heals nearby allies for 75% of the dealt to you.
Muscular Augments: Attacks become ranged
Pathogen Glands: when you shapeshift as an allied hero their mana regen is increased by 75% and their cooldowns are 25% shorter.
Reserved larva: reduces your respawn timer by 50%

The changeling is designed to confuse and trick your enemy, he specializes against AA hero's with his build in block and getting buffed when attacked. Depending on the team's needs he can be build more supportive or offensive later being able to give allies mana and health or even being able to tank for a short while.