7. Skill Order
I put my first ability point into Silver Batarang, and max it out first. The increased slow and damage, as well as the cost reduction are all essential parts of Nightmare Batman's ability to stick to his target and maintain high damage.
I put my second ability point into Bat Swarm, so that I can use it to try and get an early kill by surprising the enemy in conjunction with Psychic Assault or Super Speed. It is also helpful if the enemy has an early gank, providing an easy escape.
I put my third ability point into Savagery. In a game where I am fed or doing very well, I will often put my early points into Savagery after Silver Batarang, but if I find myself needing the shorter cooldown on Bat Swarm to get in and out of fights, I will level up Bat Swarm first. Choosing which ability to max out first is a matter of personal preference, play style, and individual game information.
I maximize Eternal Hunger last, as most of my Nightmare Batman builds include a heavy amount of Lifesteal through his items, and the ability points could be better suited in his other abilities early on.
8. Item Build
Item choice is a major decision in any MOBA. Though I list the items that I have had a lot of success with, this build is by no means the only one that will lead you to success, nor will building these items in this order be the right decision in every game. One of the key strategic points in Infinite Crisis is choosing when to build what items, and that judgment is a skill that can only be learned with practice.
The Nil Weapon is a great starting item that gives you offensive and defensive capabilities to begin the game, as well as the sustain to keep you in lane until you have saved enough credits to significantly upgrade your gear.
Choosing between each of these items is going to depend on how soon you return to base and how many credits you have access to. During a typical game I will wait until just after level 6 (and I have hopefully scored a kill) to shop.
Coda Blade- This item is a great early item for Nightmare Batman simply because it makes him do more damage. Due to his passive, this damage also equates to sustain, and will give you greater presence in lane. The later versions of Coda Blade are also very useful, so if you find yourself with some extra credits at the end of shopping, buying or upgrading this is a good way to give yourself a small boost.
Soultaker Katana- The Soultaker Katana is an item that you should buy if you find yourself with a large chunk of early money. Because it gives Nightmare Batman less initial Attack Damage than a Coda Blade, and Nightmare Batman already has powerful sustain, the most important aspect of this item is the Rank 3 Attack Damage Collector buff. If you purchase this item, quickly getting it to the Rank 3 version is essential. This item also makes Nightmare Batman highly sustainable even in intense fights, and allows him to trade damage with ease.
Claw of Horus- This is a well-balanced item for players who are looking to beef up a little bit, while still putting out powerful damage. The Claw of Horus is a core item in nearly all of my games, building on Nightmare Batman's already potent theme of making his offense his defense. This item is a good mid-range upgrade for any point in the game, so if you cannot afford to get a Soultaker Katana or Deathstroke's Claymore, this should be what you're buying.
Deathstroke's Claymore- Deathstroke's Claymore is a huge power upgrade for any phase of the game. If you are ahead, this item will make you unstoppable, and if you are behind it will help boost your damage to the point where you can go toe to toe with most opponents. If you can afford this item or its upgrade at any point, you should strongly consider purchasing it.
Kryptonian War Armor- This defensive item gives Nightmare Batman lots of protection against his biggest weakness: Power burst damage. If you find yourself getting poked down early by champions such as Green Lantern or Joker, be sure to pick this up early. Otherwise wait until the mid-game when being bulkier will be an essential aspect of surviving team fights. Getting this item up to Rank 3 or 4 early makes a big difference, as the 20% increase on Healing Received affects Nightmare Batman's sustainability. Additionally, Kryptonian War Armor is one of the few items in the game that gives Move Speed, which allows Nightmare Batman to stick to his targets even better than he normally does.
Cheetah's Claw- Cheetah's claw is a great cheap way to boost Nightmare Batman's offensive abilities. Though its early ranks are weak, they are easy to pick up on top of several more expensive items. Additionally, its max rank's ability, Desperate Speed allows Nightmare Batman to duel or escape with even greater potency.
Other Items to Consider:
Hawkman's Harness- This cheap defensive item is great for when you've got some extra change lying around after a big purchase and you want to bulk up. Even better, its max rank form is refundable, so you'll be able to trade it back in for something you need more in the late game. Though it isn't a core item in most of my builds, this item is definitely useful and worth considering.
Sword of Beowulf- As I stated above, Nightmare Batman's greatest weakness is going to be against Power burst damage. The Sword of Beowulf is perfect for countering a team of champions who can nuke you down quickly, while still providing enough offensive capabilities to keep you relevant to the game. This item should be a quick purchase if you're against a Power-ful (hah!) team, and ranked up quickly to take advantage of the Response Shield and Desperate Endurance.
Atomic Axe- This item is a pure offensive powerhouse. If you find yourself easily crushing your foes, or are looking to do as much pure damage as possible, the Atomic Axe is a great way to go. Although I don't usually build this item, it is a reasonable alternative to Deathstroke's Claymore if you're looking for a big step up in your damage.
Mega Rod- This is a situational item that is best used against teams largely comprised of melee champions. A powerful and useful item at all ranks, the Mega Rod is good for pushing lanes, or for games with lots of messy and long-lasting team fights.