Since editing is a pain in the *** on this site I'll just leave some explanations of everything:

This guide is not for beginners, since I'll not explain everything single thing. You need to be able to know about positioning team fights and so on.

1 - Talents and variations

2 - When to NOT pick tychus

3 - How to play him

4 - General Tips

Don't forget to check the 3 builds variation on the guide to have a better visualization of the best builds;

Lvl 1: This is the easiest talent to pick. You ALWAYS want to go Armor Piercing Rounds. There's no scenario where any other talent is useful.

Lvl 4: Spray 'n' Pray is usually the best choice since it will give you reach with your strongest ability in this stage of the game, and it's still useful later on.

If your team is lacking healing or you predict that you will be able to auto-attack a lot, pick Vampiric Assault.

Melting Point is acceptable on some maps like Tomb of the Spider Queen or Blackhearts Bay, since on those maps, getting high dmg on structures are usually very advantageous.

Lvl 7: Now this talent is key for which build you going. Quarterback works better with Melting Point and is very useful on team fights.

My personal favorite is Rapid Fire. Later in the game you will be a dps machine with this talent. With Vampiric Assault, Problem Solver and Nexus Frenzy you will be able to auto-attack and kill any hero extremely fast and destroy structures so fast that the other team will not be able to react.

First Aid suck. The only reason you should pick it is if you are a third assassin and there's no healer on your team. The other talents are much much better.

Lvl 10: Commandeer Odin: Best ultimate. There's no second guesses here. When you see a team fight is going to happen, use it and prepare to destroy everyone. The dmg output is outrageous.

The only Reason to pick Drakken Laser Drill is if you are in Haunted Mines and want to destroy the golem fast. Besides that, there's no reason to pick it.

Lvl 13: Pick Problem Solver if you are going for the DPS build. It's a must. If you are not, go for Lead Rain, since it's EXTREMELY powerful.

Lvl 17: Stoneskin gives you a bigger chance of survival if the other team is trying to focus you and can be a life saver in many situations. All other talents and kind...meh. Some people like Concussion Grenade, I personally find it useless.

Lvl 20: Nexus Frenzy and prepare to deal more than 600 dmg per second on your auto-attacks. If you are not going for the dps build, Bolt of the Storm is fantastic. In case you picked Drakken Laser Drill, upgrade it. Focusing Diodes is an huge improvement.

In my personal opinion, don't pick him if you are going against:

Tyrael - Huge Mobility. If he decides to focus you, you are done.

Zeratul - Annoying, extremely strong and he is not of the feel heroes that can kill you before you can kill him.

Stitches - Hooked? Dead. Nothing you can do.

Muradin (optional) - You can usually dps him down, but it's just bad to go against him with Tychus. There are a lot of better opitions.

I also don't recommend playing as Tychus if you alrdy have 2 assassins on your team, but you can use him as a specialist with the grenade Build.

Early Game: Focus on your line and bully the other heroes who stand there. If anyone can gank your line, you are set, since Overkill is the best ability in the early game.

Mid Game: Stay behind and use your ultimate before that team fights start or just at the beginning. If you are not with your ulti, always shoot the nearest hero, doesn't matter who its. The biggest trap for Tychus is entering inside the team fights. He is very squishy and can easily die trying to reach that fragile hero on the back of the enemy lines.

Late Game: When you pick Nexus Frenzy you should be able to treat tank heroes as nothing. They will die as early as any other hero. You only need to worry about staying alive and positioning yourself.