Io

Tether breaks trees which is useful at making tree line paths or optimize farming routes.

Make sure to have spare consumables with you to keep your laning partner healthy.

Look around the map for opportunities to Relocate in and prompt your teammates to setup kills.

Past laning stage, you typically want to play with your farming core to boost his farm and stack camps.

Avoid showing yourself at the start of the fight as you are number 1 target for opponents.

When using Relocate to save an ally consider relocating nearby to be able to re-engage faster.

You can use Relocate to push out a wave or rat a tower when not much is happening around the map.

Pick up Aghanim's Shard at minute 15. It provides a source of disable that opponents are typically unaware of.

Io is one of the best Cheese carriers in the game as you can extract double the value through the Tether.

Grab the healing lotus to have a burst of HP and mana regen for yourself and the tethered ally.

Someone should buy Spirit Vessel against Io to offset healing and regeneration.

Harass either Io or his laning partner, not both equally.

Relocate can be cancelled by disabling or silencing Io during channel time.

Focus Io in the fights as he's good at sustaining and saving his cores.

Gap closing items will help you get on top of Io.

Items that reduce healing and regeneration are great against Io.

Be careful about Io's ratting potential with Relocate.