Let me start this guide by saying that this will be slightly biased because i hate cheese(6 pooling in starcraft, tower rushing in age of empires, the "noob combo" back in halo, etc.) and deceiver is one of the two classes with a cheese loadout. Okay, now that we've got that through with welcome to the comprehensive deceiver guide, I'll be covering strategies, loadouts, and general tips and tricks.

This guide is a work in progress, I will be adding more soon. If you like this be sure to check out my Comprehensive Scout Guide!

The deceiver is an assassin class that depends on sneaking into an enemy team to quickly set up and execute a high value enemy and get out immediately after(unless you are being payed no mind).
Alternatively, deceiver can be a powerful support that can ruin fights with dominate mind(this however is a thankless, scoreless job best used with coordinated teams or groups). One way or another, awareness and being opportunistic are both critical. Study the enemy and be ready to strike, your timing will make or break your performance. This may seem circular and confusing, but things will clear up when i go over techniques for each loadout.

Disguise
A key ability for sneaking into enemy teams. The key however, does not lie in the disguise but the 5 seconds of TRUE invisibility prior if you hold down RMB. This is the ONLY skill in the game that grants true invisibility and is key for positioning behind an enemy. The disguise is very easy to see through because unlike humans you cannot sprint(a big factor), roll, aim or attack, therefore it is never a good idea to stay in the diguise too long, even if no one saw you fade in. The diguise will buy you 1-2 seconds while they hesitate to shoot an ally right off the bat, but that's about it. Act accordingly.
15 Second cooldown


Dominate Mind
A fantastic supporting ability that does decent damage and allows you to virtually guarentee and enemy's death when used in coordination with your team. It's main weaknesses are that you are forced to channel it and you must have vision on the target to start controlling them. While not the best skill to rack up your own points with, it can make a huge impact when you are playing with coordinated teammates

50 Damage/second
6 Second duration
20 Second cooldown


Backstab
A key tool for the assassin deceiver playstyle, also one of the most difficult spells to use effectively, landing this skill consistently is the sign of an experienced deceiver. While it's damage seems weak, it doubles when hitting an enemy from the back, making for the highest damage one-tick skill in the game, effectively sealing their fate so long as you can follow up with a few attacks.

ALWAYS REMEMBER that backstab's hitbox is on the RIGHT of your character model, as well as having a very small hitbox in general, this WILL take practice but will absolutely decimate enemies once mastered. It should also be noted that there is a slight delay and the enemy can hear your blade charging. Higher level players WILL react to this so be ready to follow their dodge as you can change direction mid cast.

275 Base damage
550 Potential damage
10 Second cooldown


Infect
Why people hate deceivers. Infect is a strong damage over time skill with a similar delay and lunge to backstab with a larger hitbox and less potential single target damage but higher guarenteed damage. It can also spread to other enemies during the 4 seconds of damage over time after the hit. Due to the visual effect, this is a GREAT anti-camo skill, and decimates grouped enemies. However when going for an assassin playstyle, backstab will yield more returns.

205 Base damage
50 Damage/second------(These two factors spread to nearby targets during those 4 seconds)
4 Second duration-------|
405 Total single target damage
15 Second cooldown


Illusions
Hides you for a split second in a black cloud and summons two non-damaging illusions of yourself at 1/5 of your maximum hp(somewhere around 202-211hp). You and your clones will be all black for the duration, however your clones tend to run straight at the enemy and attack slowly and/or walk in awkward patterns, so this is best used to have them body block, mask a quick escape or(offensively) to rush a(non alchemist!) seperated enemy and confuse them with a flurry o attacks from you and your clones. Altogether a versatile spell useful in many situations.

~200 Illusion health
8 Second duration
20 Secod cooldown


Shroud
I like to refer to this skill as a jack of all trades, master of none. It masks your presence decently, does decent damage, and is okay for escape. That being said, it is an extremely versatile and useful skill, it can be used to sneakily finish off an enemy, run through and confuse a team getting some good poke as you run out, or just for flat escape so long as you dodge around a bit, making it hard to track you. This skill makes you see through but by no means invisible, so when attempting to escape, act as if they could see you plain as day, because experienced players can. (NOTE: THIS ABILITY WILL SHED BOLA AT VIRTUALLY NO COST ACTIVATE WHILE UNDER THE EFFECTS OF BOLA)

200 Damage/second(note: you have to be literally humping them to acheive this, in which case you will usually either get wrecked by them if they are a prophet or vanguard, or their team otherwise)
6 Second duration
25 Second cooldown

This is my favored and most experienced class. The loadout is as follows: disguise, Backstab(required), and either shroud or illusions. As mentioned before disguise's strong point is in it's 5 seconds of true invisibility, this is your key to the back of the enemy team, on your way there be looking for enemies offset from the group, a scout charging his bow, a hunter taking pot shots at your teammates, anyone apart from their team or out of direct line of sight of their teammates(enemies using healing stations are prime targets!). If your invis runs out, your disguise will earn a few extra seconds if no one sees you fade in. Higher level players will notice either that they have an extra teammate or that you're not sprinting dodging aiming or firing and immediately spy-check you(a team fortress 2 term for shooting you in the face to see if you're a fake) so if you're not doing anything 3-4 seconds after fading in, back out and try again.

This is the part you'll need to practice with, once you're set up behind your target, your Backstab has a slight delay and ---originates from your right hand and WILL NOT sweep across--- so make sure you set up on the left side of them and adjust as they move.

At this point they're three hits from a death, either you can get those in addition enough or they'll run to their team, this is where you'll have to use your judgement. One way or the other you want to pull your escape skill, you can either use it to dive in and finish your target(with illusion, be quick and aggressive, if you don't finish in 3-4 seconds, get out before they lock you down and rip you a new one. If you have shroud, cast it and dodge around, following your target. Shroud should bring them down about one hit's worth in a few seconds, finish them with a strike and get out asap. Same rule applies, if you can't get it done in 4-5seconds, get out.) Alternatively, you could back up and wait for your cooldowns. Be rational, you'll always want to take the first option, but restraining can win you a fight soon after and prevent a suicide.

You'll run into situations where your escape skills are on cooldown but your Backstab is up, use good judgement, if there's someone on the outskirts you can kill in one to 4 or 5 seconds without taking too much damage, go for it. But if your team is getting their asses handed to them and there's nothing you can do, back out and wait for the next fight. NOTE: THIS PARAGRAPH APPLIES TO ALL DECEIVER CLASSES

That's just about it, simple objective that's difficult to complete, with practice you'll be racking up the kills.

The plague bringer is similar to the hitman, but your goal is almost the opposite(unless you picked this to pick off a camo scout). The loadout is: disguise, infect, shroud/illusions. Your job is to spread the plague and wreak havoc. This is best used during an engage on a group of close enemies, or someone likely to get close to their allies(vanguards, prophets, alchemists). Executed well, you'll infect 3 people resulting in 205+200+200+200= 805 damage for pressing q and being decently accurate. From there you can press attacks if they don't focus you, or pull your escape move to let your team finish the job and rejoin later to clean up some kills. You can also use this as a weak engage, but you'll be forced to take the retreat and rejoin option every time, you're not a tyrant.

Let me start this one by saying it is not a solo queue class and if you're with a team coordinated enough to utilize this odds are you don't need the majority of this guide, so I'm only going to touch on this. The loadout should be as follows: Dominate mind, infect, shroud/illusions. Your goal is to possess a high value enemy and force them to kill themselves, either turning them into a punching bag or running them into a choking haze, etc. You COULD use this to pull an enemy to you but this is rarely as effective as Hitman or Plague-bringer.

The main thing to remember is that you need line of sight and you're stationary, meaning they will be able to see you and have free shots. You're going to want to position behind them or somewhere unexpected as well as possess the target soon after or in synch with an engage so you don't die or have to cancel your channel. After your target dies or the skill expires, either jump in and try to get a good infect off or back out if it's a lost fight.

This is not to say one coud not pull off a solo-kill based Dominate mind deceiver, but it is more reliably used with coordination from other teammates, as the skill can be very lackluster alone.

I'm not giving a guide on this, I'm showing why it's bad and you shouldn't invest time in learning it(as if it takes much to learn) and why it gets ruined so easily. The loadout is disguise, infect, shroud. Similar to Hitman, you pick out a target, infect them, shroud and run circles around them and finish them with a melee attack. Sounds effective, but it has one huge flaw and this is why it is cheese. You spend the entire shroud duration following and running around your target, and by NO MEANS are you that hard to see, you WILL get wrecked by any human team in higher elo because you send a minimum of 6 seconds executing this, more than enough time for an alchemist or hunter 10 feet away to rip you a new one and save their teammate with no problems. This WILL NOT make you do well once you face savvy players and is NOT a strong playstyle. Don't invest in it.

That's all I've got for now, if you'd like video supplements(like I did in my scout guide), leave a comment. Thanks again, happy hunting!

P.S. If you liked this guide, and would like to see another, leave a comment below. I have other ones in mind bont don't really see a reason to make them at this time(they're a lot of work).