How to deal with Magnus?

Me and my team get destroyed by Magnus and we have no idea how to counter him. Its awful. Please help.

Good positioning is the only way you can coutner Magnus,and counter-initiation.Keep your big AoE nuke behind everyone,even if he catches all 4 of you,you will have that Tidehunter/ Naga Siren/ Enigma/ Elder Titan/big AoE ult that can counter initiate and probably win.

Or you can initiate on him, and make sure he is stunned/silenced and kill him fast. I've had one game where I was Silencer, and after a few teamfights of Magnus wiping us I came up with the idea for me to ulti and we would run in and focus Magnus first, before he could do anything.

Radiance disables blink, queue a stun on him right before u think he will blink, for example, hexes have instant cast time. Having a good Rubick is nice as well. Or just initiate before he does. If it is really bad, ban him.

That is only if you can kill him,there are 4 more teammates right next to him.

Find a good Rubick player.
Find a really good Clockwerk player.
Get an Orchid on Qop or Storm Spirit.
Use Batrider.
Use Warlock.
Don't bunch up.
Etc etc

The options are endless

Batrider and Rubick are most standard counters I think.

There are plenty of ways to shut down Magnus. First, you have to have a decent team composition and you must have a pretty powerful mid hero that could shut down ol' Magnus, such as Queen of Pain, Puck and Rubick. In the mid game, teamfights start to break out and Magnus is very powerful at this stage of the game. When the teamfight is about to start, always mind your positioning and never clump up, because that's just what Magnus wants your team to do. If possible, initiate first and focus down Magnus with stuns and silences so that he won't be able to do anything. It would also be good to gank Magnus and kill him with your gankers, then force a teamfight or take a tower, because the enemy team won't be able to do anything without Magnus unless they have another good initiator like Enigma, Earthshaker and Tidehunter although it is very unlikely. If you follow all of these steps, you should be able to win the late game with your hard carry, but always remain cautious and never neglect the presence of Magnus. Another interesting way to counter Magnus would be to pick Rubick and steal his Reverse Polarity, then let him have a taste of his own medicine, just like the same way Rubick counters Enigma by stealing Black Hole. But the only surefire way to counter any hero is practice, so don't forget to do so!