After playing with this new champ non-stop since his release I have enough confidence to make a good guide for anyone wanting to Jungle with this beast. If you have any questions, concerns or feedback send me a message or leave a comment so I can imporve the guide.

While his ratio's are much lower than Shazam's his builds and paths are very similar. I have a Shazam guide in which I have way more games in here. So if you see some crossover that's why. PLEASE READ THE SPECIAL NOTE ON HIS PASSIVE!!!

So lets get started:

CRIMSON SLASH (Q)

For 5 seconds, Atrocitus' next Basic Attack deals an additional 35 Power Damage and the target loses 25%Move Speed for 2 seconds.

Enraged: The power damage and slow is applied to all enemies in an area around the target.

Using this skill resets your Basic Attack Cooldown.
Damage:35  60  85  110+ 35% Power Damage
Slow:25%  30%  35%  40%

This Ability is going to be your main ability to clear camps and gank. I know the taunt seems like it would be more useful to level faster but only the enraged version scales the time of the lock down. His Q scales the slow regardless if enraged or not. Plus this combined with your passive will make your clear speed very fast. Remember it resets your auto attack speed so always use it right after and auto attack to maximize your dps. 

COME AT ME (W)

Atrocitus Taunts nearby drones and creatures and gains flat damage reduction of 2 for 4 seconds. For each 10% missing health, he gains 0.5 bonus damage reduction.

Enraged: While Come At Me is active, Red Lantern's Rage can deal damage every 0.5 seconds.

Dmg Reduction:  2  3  4  5 

Bonus Dmg Red:  0.5  0.8  1.1  1.4  Cooldown:  15  14  13  12

This has a lot of utility but not much else. The damage reduction combined with your early marauder shield will make sure you will stay up while jungling. Here are a few uses for it in specific situations: Pulling minions from agroing onto your carries. Pulling minions out of the enemy turret range so your team can clear them. Pulling minions closer to your tower. taunting minions on to you instead of your tower. And my favorite when pushing down a tower pulling enemy minions to you instead of your minions so your minions last longer against the tower. If you wait until its enraged the passive will trigger quick enough to help clear the wave fast. 

OVERWHELMING RAGE (E)

Atrocitus fills target Champion with rage, forcing them to charge at him while he charges toward them, and dealing 40 Power Damage when they collide.

Enraged: Instead of dealing Power Damage, Atrocitus and his target are Taunted to each other for 0.65seconds after colliding, with their Attack Speed maxed and -75% Attack Damage.

Damage:40  65  90  115+ 40% Power Damage
Duration:0.65  0.80  0.95  1.10

This is a very dangerous ability and I wager the one he's most known for. Its use is obvious  and should be leveled behind his Q. You will be tempted to open with this but try and wait to catch them when they try and run. I will cover more on this on my Jungle / gank portion of the guide. 

PLASMA WAVE (R)

Atrocitus spews a wave of plasma, increasing enemy's incoming damage by 15% and dealing 160 Power Damage over 6 seconds. For each Champion hit, Atrocitus gains 20 Rage.

Damage:160  220  280  340+ 60% Power Damage

Several uses. Obviously good to open with but will be a waste if you use it without any follow up. So be sure your team is in a position to add damage right after ward. Remember it gains rage when it hits enemies. So if you are just shy of 50 use it, enraged E, Q. It also does damage of time so if you're going lose a kill on some who is super low hit them with it and wait for the kill indicator. 

RED LANTERN'S RAGE (PASSIVE)

Atrocitus gains 5 Rage when he Basic Attacks or when damaged by enemies. He becomes Enraged at 50 or more Rage, adding bonus effects to his basic skills, which then cost 50 Rage to use. After 10 seconds without gaining Rage, 2.5 Rage will be lost per second.

Atrocitus deals 20 Power Damage to nearby enemies each time he is damaged, up to once every 2 seconds.

Damage:20  40  60  80+ 10% Power Damage

SPECIAL NOTE: If your passive does damage to an enemy champ under their tower you will draw agro. They plan on fixing this but for now this is a huge concern. Don't be under the tower when an enemy shows up. 

This passive will help clear camps so make sure to stand in the middle of the camp while you clear it. When I cover jungle pathing later I will elborate a little more. It's damage towards the end and its bad ratio makes it less than ideal to max early. 

STOLEN POWERS

As a jungle your ability to gank and control objectives will determine whether you're a great jungler or just the jungler. I chose the two stolen powers for these reasons.

Choose detonate over consume every time. It has a long range which allows for steals. That alone makes it better. If the enemy is trying for EMP and you are there they risk the steal without retaliation. Other than EMP use it on big camps early game to help clear time and prevent damage from tanking it for so long. I prefer Joker's detonate for the slow utility. I have secured too many kills with the slow to use anything else.  By blowing up a meteor or a minion to slow/damage an enemy to get them back in range of my abilities it nullifies any benefit the others have. 

Catwoman's Teleport is only 2000 merit now. No excuse for not having it. Use your teleport to magnify your presence in lanes. One of the best ways to use it is to gank bot, take emp. Then, leave their line of sight and port top. They just saw you bot and will not expect you to be there. Get another gank and another EMP. If you use your port and you don't a) get a kill with follow up results b) protect/secure an objective c) join a team fight while split pushing... you're wasting it. Getting one kill and doing nothing after that is not worth a 5 minute cool down. 

The others either don't synergize well with Atrocitus and/or aren't valuable enough to the team to take and trump either detonate or teleport. Being there now is more important than having another power and not being there in time. But just to list a few specific examples.... Alternates and why not: 

Invulnerable: It seems like a good idea. But not worth giving up Tele and jungling without det is just dumb.

Physic Assault / super strength : You have enough CC and wave clear. Done.

Super Speed: Might be useful but again not worth tele. 

ITEMS

I use flat HP for my Aug's. Specifically: WOLF, TSUNAMI, SPEED, CASTLE . I use the following Mods: Discounted Marauder Shield, Empowered Ra's al Ghul's Robe, and Empowered Atlantean Royal Seal. The reasons are explained in the build order of the guide below.

Starting Items: Marauders Shield tier 2 (Modded for 100 credits off at tier 1) and 2 health pots. You may be tempted to use tier 1 ring and shield with 3 pots. If your going to be using all of your mods for other things and you have a team that will hard leash then I can understand. But tier 2 Shield is very strong right now. Its better than the other marauder items in every way as it is right now. Don't bother upgrading it as you're going to sell it later and its very useful at tier 2.

Early Items: Atlanteans Seal (Modded for the extra slow). Health, plus Power damage, plus slow. No brainer. Your Q and E are single target abilities and this will make your Q super effective.  Now lets look at what enemy is building and how well you're doing. If the main damage is coming from AD go with booster gold's suit. The HP will continue to ensure you're always at a gankable hp level and the CDR will start to let you use your abilites more often in a team fight. If the main damage is coming from PD then go for Helm of Fate. This will get your damage up but make you hard to turn on when ganking their PD carry.

Mid game Items:  Ra's Al Ghuls (Modded with empowered lazarus effect). Will be picked up after your first defensive item be it boosters or Helm. This item while modded is OP atm. Unless you die under turret and there are no teammates around its next to impossible to die while the cool down is up. Abuse this in team fights by baiting the enemy to over commit. 

Mid to late transition: Next pick up then opposite item listed in early game. If you got Booster's now get Helm and visa versa. If the enemy has a heavy AD presence get nerons contract. This combined with Ra's will make you extremely hard to deal with. If the enemy has good power damage at this point you can add Kryptonian War armor.  

You should generally finish the item you are currently building. The exception is if you're building attack/power armor (boosters) and you realize their AD/PD champ fell off due to being shut down or w/e now your main concern is the other type of armor. In this case you can stop mid way through the item and build the different item (Helm) as needed. But honestly if the enemy has a decent mix of damage you can start with Ra's after Seal. And honestly this is not a bad idea to just start with. 

Late game: So by this point you should be able to survive in a team fight and have enough damage to not be ignored. If the enemy has built a decent amount of HP and/or has a bruiser/tanky comp go for Cosmic Staff. If not Fatality's Energy Lance is going to give you some punch plus add to the CDR from booster's. If the reast of your team is killing easily consider Pandora's box for the CDR, move speed and PD. The active is ok, but without the mod you really have to be selective in it's use. 

PUTTING IT ALL TOGETHER

Early Game

Now if you're new to jungling, don't do anything fancy. Start at HP camp, go to side lane camp and then go to lane to get EMP. Ask for a hard leash on the HP camp. Try not to use your detonate on the first HP camp. This will leave it available if you need it for EMP. Make your way to the mid lane jungle camps. On your first pass skip the camp with the 2 strong bots. This early, they take too much time, deal too much damage and don't give enough XP to be worth the time. Grab the 3 bot camp and you should be lvl 3 by then. Go to speed camp, use detonate here and then work your way to the other emp after the last side camp is cleared. 

How to clear a camp: Place yourself in the middle of the mob. Auto the big mob, use Q immediately to reset attack. Auto attack each small minion once (twice on the first pass). Once rage is built up use Q on big mob. This method is focused on clearing the camp in the most time effective manner. You don't waste time auto attacking a minion that can be killed by a passive or a splash Q. Once you have W use that to start so you can reduce incoming damage unless you have an enraged Q to start.

Ganking: Walk in behind the enemy. The aim is to auto, until they react, Q, Auto, then E as they get away from your melee range. Of course if your laners need the CC as soon as possible taunt as you come in and be sure to save the rage for the taunt.  This is so you can keep the enemy locked down as effecently as possible.

You change this jungle path pattern after the first EMP for two reasons. 1) The enemy is trying to take the other EMP. Use tele if you can get there in time to make a difference. If there are no cams close by this will not be likely. Don't waste the tele otherwise. If their jungle is there go steal a camp if it suits you. 2) The enemy mid/opposite lane you are at are in a prime gank situation. (50% or less HP, over extended and your laners are in good condition to engage with you). Early put a bigger urgency on ganking side lanes in order to get emps. 

Go back if there isn't much for you to do at this point. This is to grab the emp back at base. If you are up on your timers you shouldn't waste an emp grab by already having a tier 2 EMP at base. Use them and use them often. Keep that pressure up and make your presence felt. 

If your tele is up don't be afraid to split push so long as you have vision of the majority of the enemy team and your team is pushing elsewhere.  Of course if your team can't disengage very well and are relativity squishy this should be done with extreme caution or encourage someone with good escape to split push while you safe guard the team.  

Late Game / Team Fights

When the fight is engaged and you weren't the initiator go straight for carry's. If they initiate on you peel for your carries and let them kite. Don't forget to use your ult to spay as much of the team as possible. The best way to get this done is immediately after you get initiated by the enemy team. They will colapse on a target giving you a perfect shot. The 15% extra damage plus damage over time can easily swing the early fight in your favor. Atrocitus doesn't have a lot in mobility but has excelent peel. So he doesn't make for a great initiator but once the fight is going your priority is to peel threats off of your carries and then if it looks like they got it handled disrupt the enemy carries.