Incohatus the Formless mini-guide (by Overflow)

Well, since there's so many interest about Incohatus the Formles, i will include Overflow_GR's mini guide here. This guide is covering some aspect of Incohatus. But importantly, this mini guide provide list of hero skills that you can/cannot copy or some restriction and even abuse :D

Incohatus has no permanent form, but has learned to adapt to the ever-changing field of battle. He has the ability to replicate most spells perfectly, allowing him to use other heroes' abilities against themselves. With this strategy, Incohatus opens up a whole new world of possibilities, allowing him to take the best and worst of all the abilities his allies and enemies have to offer.

Strength - 15 + 1.5
Agility - 14 + 1.3
Intelligence - 27 + 3.5
Attack range of 500.
Movement speed of 300.

There are 3 important things to remember about his skills.

1) The level of the skill copied depends completely on Formless' own skill level. If Formless has a level 4 Unus and uses it on Pudge, it gets a level 4 Meat Hook even if Pudge hasn't fully upgraded it (or even learned it at all).

2) Don't copy skills that use the same base skill. Having both Arc Lightning and Laguna Blade in your skillset will result in using Arc Lightning when trying to use Laguna Blade if both skills are ready.

3) Denique is upgraded with Aghanim's Scepter. Definitely something to consider if there's a powerful ultimate in the game (think Witch Doctor).

Skill build
You should determine your skill build/item build/strategy based directly on ally and enemy hero picks.

Item build
The only items that are always good for Formless are Boots, Bracers/Nulls, Guinsoo's. Anything else is luxury and up to your own judgment of each game.

Combos!
The possibilities are endless. Even if you don't think that your allies and enemies have skills worth copying, you'll be amazed at the results of some combinations. You don't have to learn something as crazy as Meat Hook - Blink - Maledict - Rupture to be effective.

Uncopied Skills (you cannot copy these skills)
* Impetus
* Morph (old & new)
* Great Cleave
* Synergy
* True Form
* Moon Glaive
* Take Aim
* Berserker Rage
* Quill Spray
* Bristleback
* Warpath
* Primal Split
* Dragon's Blood
* Elder Dragon Form
* Spell Shield
* Glaives of Wisdom
* Last Word
* Spirit Form
* Multicast
* Phantom Edge
* Grow
* Chemical Rage
* Overload
* Burning Spear
* Berserker's Blood
* Refraction
* Meld (copying this gives you a permanent passive +20% ms skill that you can't get rid of blink.gif)
* Psionic Blades
* Tidebringer
* Split Shot (new)
* Crippling Fear
* Hunter in the Night
* Devour
* Backtrack
* Corrosive Skin
* Storm Seeker
* Feast (old & new)
* Infest
* Metamorphosis
* Witchcraft
* Mighty Swing
* Soul Assumption
* Gravekeeper's Cloak
* Shapeshift
* Blur
* Kraken Shell
* Anchor Smash
* Flesh Heap
* Geminate Attack
* Time Lapse
* Shadowraze
* Necromastery
* Presence of the Dark Lord
* Requiem of Souls
* Strygwyr's Thirst
* Frostmourne
* Borrowed Time
* Dispersion (old & new)
* Arcane Orb
* Essence Aura
* Poof
* Divided We Stand
* Heartstopper Aura
* Quas (old & new)
* Wex (old & new)
* Exort (old & new)
* Invoke (old & new)
* Spellsteal
* Permanent Invisibility (old)
* Death Ward (old)
* Necrogenesis
* Ante Up
* Pulverize
* Fly

Shared skills (the skill is using same base skill, hence using one of them result on using both of them)

Storm Bolt based
* Magic Missile
* Lightning Bolt
* Storm Bolt
* Omnislash
* Fireblast
* Assassinate
* Dragon Tail
* Mana Void
* Primal Roar
* Void
* Open Wounds
* Reaper's Scythe
* Poison Touch
* Time Void

Forked Lightning based
* Nether Swap
* Forked Lightning

Chain Lightning based
* Arc Lightning
* Laguna Blade
* Wrath of Nature
* Lightning Storm
* Chain Lightning
* Brain Sap
* Charge of Darkness
* Culling Blade
* Aphotic Shield
* Paralyzing Casks
* Astral Imprisonment

Thunder Clap based
* Thundergod's Wrath
* Earthshock
* Thunder Clap

Locust Swarm based
* Nature's Attendants
* Exorcism

Carrion Swarm based
* Waveform
* Dragon Slave
* Wild Axes
* Dual Breath
* Lightning Grapple
* Carrion Swarm
* Sonic Wave
* Timewalk
* Tidal Wave

Acid Bomb Based
* Adaptive Strike
* Curse of the Silent
* Ignite (old)
* Gush
* Ignite (new)

Mirror Image based
* Mirror Image
* Phantasm

Fan of Knives based
* Echo Slam
* Heat Seeking Missile
* Scream of Pain
* Death Pulse

Blizzard based
* Smoke Screen
* Avalanche
* Scattershot
* Acid Spray
* Dream Coil
* Rocket Flare
* Torrent
* Maledict
* Sanity's Eclipse
* Upheaval
* Earthbind
* Weave
* Expulsion
* Vacuum

Summon Bear based
* Summon Spirit Bear
* Diabolic Edict
* Poison Nova
* Nether Ward

Bloodlust based
* Rabid
* Bloodlust
* Surge

Berserk based
* Ultimate
* Enrage
* Rampage
* Sprint
* Strafe
* Frenzy

Inner Fire based
* Living Armor
* Dark Ritual
* Empower
* Death Pact
* Enfeeble

Charm based
* Conversion
* Holy Persuasion
* Epicenter (WTF, this should be in Channel blink.gif)

Drunken Haze based
* Laser
* Penitence
* Drunken Haze
* Incapacitating Bite (buffing issue)

Windwalk based
* Doppelwalk
* Wind Walk
* Leap
* Vendetta
* Shukuchi

Cripple based
* Sprout
* Sunder
* Grave Chill

Serpent Ward based
* Remote Mines
* Mass Serpent Wards
* Plague Ward

Firebolt based
* Lucent Beam
* Double Edge
* Chaos Bolt
* Lvl? Death
* Flameshot

Aerial Shackles based
* Shackles
* Fiend's Grip
* Dismember

War Stomp based
* Hoof Stomp
* Reverse Polarity
* Slithereen Crush
* Ravage
* War Stomp

Breath of Fire based
* Breathe Fire
* Ice Path

Frost Armor based
* Purification
* Frost Armor

Shockwave based
* Macropyre
* Shockwave

Immolation based (note: You can activate them all and get all their benefits, but only one of them will be dealing damage)
* Electric Rave
* Pulse Nova
* Rot
* Voodoo Restoration

Drain Life/Mana based
* Soul Steal
* Mana Drain
* Life Drain

Inferno based
* Split Earth
* Spin Web

Sleep based
* Chain Frost
* Nightmare

Carrion Beetles based
* Raise Revenant
* Watcher
* Carrion Beetles

Rain of Fire based
* Firestorm
* Fire Storm

Channel based (1st category)
* Freezing Field
* Song of the Siren
* Fissure
* Blink Strike
* Global Silence
* Overgrowth
* Midnight Pulse
* Illuminate
* Rearm
* Toss
* Hand of God
* Eclipse
* Viscous Nasal Goo
* Unstable Concoction
* Starfall
* Waning Rift
* Battery Assault
* Conjure Image
* Howl
* Meat Hook
* Nether Strike
* Burrowstrike
* Berserker's Call
* Dark Rift

Channel based (2nd category)
* Malefice
* Mana Leak
* Elune's Arrow
* Illusory Orb
* Powershot
* Ghost Ship
* Stifling Dagger
* Death Coil
* Spectral Dagger

Channel based (3rd category)
* March of the Machines
* Psionic Trap
* Wall of Replica

Channel based (4th category)
* Test of Faith
* Inner Vitality
* Fatal Bonds
* Plague
* Ion Shell

Hope this can help you guys :)
Source: Overflow's mini-guide to Formless