IO according to lore is as old as the Dota Universe (with Elder Titan been tied to him).

As of 12/15/2024 his innate is really the biggest nerf Valve has given him.

He is Position 5 (preferred) but also 4 (annoying to the enemy safe lane)

SOME TIPS:

1. DO NOT BUY HIM HIM BOOTS OR YOU CLEARLY DONT KNOW HIM.
2. TETHER IS YOUR ENTRY TO BATTLE AND EXIT, IF YOU HAVE ENCH OR CHEN, TELL THEM TO KEEP A CREEP NEARBY YOU TO EXIT.
3. IF YOUR TETHERED ALLY (PREFERABLY SAFE OR OFFLANE) IS A LITTLE FRIGGING (yk), YOUR HERO JUST BECAME USELESS.
4. YOU NEED TO BE AWARE OF YOU SURROUNDING DURING A FIGHT, KEEP BACK, BUT TRY TO HIT.

AT LOW MMR:
1. PEOPLE NEVER TARGET HIM IN FIGHTS (UNTIL THEIR BRAIN TURNS ON)
2. PEOPLE DONT LOOK MUCH AT THE MAP (You can relocate to their faces and kill them).
3. YOU ALLIES HAVE NO CLUE WHAT YOU DO SO THEY NEVER FIGHT ON OVERCHARGE, GET NEAR YOU, OR POINT 2.

AT HIGH MMR:
1. People might be smarter, so they will target you. (Position you to enter with tether, let cores look for you)
2. Relocate will be shown to enemies, so make nuking them only if you know you are not in danger.
3. So far the biggest counter I found where (Lich, Winter Wivern, Doom, Shadow Demon, SkyWrath). Ban them with your party.

Current the Facet 1 (Kritzkreig) is really good, Medigun is not as powerful lategame, but, I could be wrong since I dont use it.