The Dual-Face Io - Dual Boot and Mobile Fountain

Introduction

Io is one of the best (if not the best) supports in the game. Health regen, mana regen, attack speed increase, slowing the enemies, scouting an area, Io does everything a team would like from a support.
Oh, she (I like to think of Io as she) can also ward. Just so you know. In fact, using the ultimate, you can drop wards in pretty interesting places, making her one of the best warders as well.

However, unlike most supports who're burst support (if there's any such term) - they simply come, cast some stuff, use a few items and stay away, Io needs to practically coordinate with the carry/tethered unit, as synergy is must to make the most out of her.

Finally, this is my first guide on DotaFire (I was working on another, but found one with the same ideas, so ditched it), and will be updated in time. Feedback is appreciated.

There are two major builds for my Io now, and they're discussed below.

Pros / Cons

Pros:

[*] Regen
[*] Regen
[*] REGEN!
[*] Slow
[*] Portability
[*] Escape (More on this later)


Cons:

[*] No damage (The second skill, even if all of it lands, is the only dent you can make)
[*] No solo utility (The only thing you can do in 1v1 is run)
[*] Team Reliant (Trash unless someone works with you, preferably every one)

Skills

Tether - "Tether yourself to an allied unit or hero, granting both of you bonus movement speed. When you restore health or mana, your target gains 1.5 times the amount. Any enemy unit that crosses the tether is slowed. The tether breaks when the allied unit moves too far away, or Io cancels the tether."
Range: 1800
Maximum Radius: 900
Tether Duration: 12
Slow Amount: -100% Movespeed/-100% Attack speed
Slow Duration: 0.75/1.25/1.75/2.25
Bonus Movement Speed: 17%
Mana Cost: 40
Cooldown: 12

Your first, best, unique, beautiful skill that has reduced infinite manly men to tears (some of happiness, some...not so much). Essentially, a skill with a gigantic range (1800), is essentially just a simple hook (its NOT like Morphling's Waveform, which dodges everything - you can still get stuck in Chronosphere if you try to cross it using this, for example). Any enemy unit that touches the Tether link is slowed, both in attack speed and move speed, by 100%, which makes it very effective against right clickers. Remember the comparatively smaller range for break. Crosses impassable terrain, breaks trees and is badass in general.
IMPORTANT: Your regen WILL NOT BE transferred if you're at full HP. Use E to bypass that.
*NOTE: You can also use this to escape. Any allied units includes creeps. So if there is one in range (esp if there's impassable terrain somewhere in the way), link and escape.

Spirits - Summon five spirits that dance in a circle around Io, damaging all that they hit around you. If a spirit hits an enemy hero, it explodes, damaging all enemy units in an area around it. Creeps take minor damage from touching a spirit, but don't cause them to explode.
Radius of explosion: 300
Duration: 19
Damage to Heroes: 25/50/75/100
Damage to non-Heroes: 8/14/20/26
Mana Cost: 120/130/140/150
Cooldown: 20/18/16/14

Summons five spirits, one by one, very close around you. This does negligible damage unless more than 2 hit, but if you increase its radius slowly, it can hit and detect heroes, even if they're invisible. Great tool to check behind trees, counter a counter gank etc.
Another way is to use this, then tether to a melee hero, go close to the enemy he's fighting. Slow AND damage from all five spirits.

Overcharge - o gains bonus attack speed and damage reduction, at the cost of draining HP and mana per second. If Io is Tethered to an ally, that unit also gains the bonuses.
Bonus Attack Speed: 40/50/60/70
Incoming Damage Reduction: 5%/10%/15%/20%
HP/Mana Drain: 4.5% of current HP/Mana

Simple, underestimated and powerful skill. The one level is gotten earlier because +40 AS is a lot, but most levels are saved for later because you aren't tanky enough to sustain this. The 20% damage reduction is insane late game. Just stick it to your right clicking hero and watch the rampage.
*Note: Use this to reduce your health so that your regen is passed along.

Relocate - Teleport yourself and any tethered ally to any location on the map. After the spell expires you and any tethered ally will return to where you teleported from.
Range: Global
Delay before teleport: 2.5/2.25/2
Duration: 12
Mana Cost: 100
Cooldown: 90/75/60

Your ultimate, a game changing skill. You can teleport ANYWHERE on the map. Set up wards, insane ganks (ever seen a tether PA drop on your head as you were heading back to your tower after that over-harass?), great escapes (tether and go to base), wonderful rescues (drop in, regen, tether, take the most important hero back with you), and be a fountain (drop in, tether, mek, soul ring, pipe and leave).
You can summon spirits before you leave, to arrive with some damage and detection.
*Note: While escaping, try to use this from inside trees, so that when you come back, you live too.
IMPORTANT: It is NOT channeled. You can move, tether, cast, dance, fart, and be yourself in the 2 seconds you have.

Items

Io's items are mostly self explanatory. Since tether gives bonus regen to tethered unit, always use your actives whenever tethered, if possible. Here's an overview of the two builds:

Build #1

This is the Dual-Boot setup, and I essentially thought that if I could pull this off on Spectre, why not on Io (though the boot combination is different)?
*Note: This will work extremely well with a Rubick in your team, since his Null Field essentially makes the lack of Pipe of Insight inconsequential.

Remember, the Purchase Order is important. Here is why:

Early Game

Ring of Regen and not Ring of Protection - Since your Tranquil Boots will be delayed this time, you want something else for Tether regen, and this is it. Plus, you don't take enough hits to make early armor worthwhile.

Arcane Boots and not Soul Ring - This reduces no health on you, is AoE, so it means everyone will get it in teamfights, while your Tethered unit will recieve (135+202.5=) 337.5 mana. Usually enough to pull off any 1 spell, which is better than a single unit regen offered by Soul Ring which gives just 225 mana to a single unit and no AoE regen. However, it costs more.

Tranquil Boots - Since you aren't trading many hits, this will mostly be active. Meaning tons of regen for your tethered unit. 15 free HP regen, not counting your base regen.

Mid and Late Game

Mekansm - Your bread and butter item. Tether and use for wonderfully rejuvenating effects. Also, your ult allows you to drop in, tether, Mek, Soul Ring, and break tether (if things are looking feasible) and head back; or take em back if things are bad (the mek will ensure those 12 seconds pass without deaths). The hero won't ever forget you. - It gives 625 HP to your Tethered unit, 250 HP to everyone.

Medallion of Courage - I've found this to be a useful item. Since you don't really go 1v1, the armor reduction on you isn't much of an issue. But it hurts the other team's carry a lot. With this and Overcharge, be an Assault Cuirass for atleast one unit (You have more AS than it, though).

Bloodstone and Heart of Tarrasque - Same as before.

This is more of a nuke revival project, where you pop in almost every item in a team fight, with your tethered unit completely being revived for Mana and HP, while the rest of your team gets a lot of regen too. This also adds some extra presence with the - Armor effect.

The other items this time around are:

Pipe of Insight - More HP regen. Also, an active that mitigates Magic Damage. With this and Mek, make everyone a tank.

Force Staff - To pull heroes closer, push enemies away (or close), position, and be more pain in the ***. Also, cheap.

Eul's Scepter of Divinity - Another disable, cheap and effective. +40 MS is helpful too, esp if Tranquil Boots are off CD.

Veil of Discord - If you have a lot of magic users on your team and some free gold, build this and spare them the expense.

Build 2

Beginning

Tango - You won't be last hitting, or foraying far early game. This'll mitigate the little damage you receive. The regen is boosted by tether.

Animal Courier - Because each team needs one.

Ring of Protection - Some armor to build into your Tranqs

Early Game

Tranquil Boots - Same as Before.

Soul Ring - Tether and use, your tranqs will regen ASAP anyway. 'Nuff said.

Core

Mekansm - Same as Before.

Pipe of Insight - More HP regen. Also, an active that mitigates Magic Damage. With this and Mek, make everyone a tank.

Bloodstone - MORE REGEN! And on the off chance you die, you come back faster. What more do you want?

Heart of Tarrasque - With this and tether, you pretty much outstrip the fountain. Welcome to regen heaven. *This is only built after everything above it has been built.

Other items

If you still (for some reason) have tons of gold and good charges on the Bloodstone (otherwise, save for Buyback), then you can buy these:

Force Staff - Same as Before.

Eul's Scepter of Divinity - Same as Before

Scythe of Vyse - Nothing like murdering chickens while you heal like Wolverine. Combine with tether ult regen and watch people ragequit.

Orchid Malevolence - Silence.

Creeping / Jungling

Samukobo brought this to my attention, so I first thank him.

If you're laning with a melee hero, any creeps that he can't possibly take (possible harass etc) is yours to last hit. The timing will take some practice getting used to as your attack has decent travel time.
tl;dr - Last hit when your lane partner can't/

Jungling:

Jungling on Io is an interesting concept. This will work with Build #2 (currently WIP), and relies on early leveling of Spirits, buying Arcane Boots instead of Tranquil Boots and creep stacking.

How to : This needs you in the safe lane (which is likely where you will be, considering your carry will take it, and you'll support him). Make sure that you stack the creep pulling camp, irrespective of whether you're pulling or not. Also, since Io is ranged, creep pulling is easy. Remember that Neutral Creeps have 7 second agro time, so time properly (should I add a brief section on creep pulling and camp stacking? respond in comments please). Then, just pull one creep wave, let them tank, while you summon Spirits to dish out some serious damage (at high levels of the skill anyway). Let your carry last hit if they need it, otherwise it's your gold.

Summary

This is a basic build, WIP.

List of things to be added:

1. Videos of each skill in use, and various uses.

2. Wall of text describing skill usage techniques.

3. Synergies and Counters

4. Teamwork Section

Thanks for reading! Feedback is appreciated!