This is the first build that I have decided to publish, as I believe I could give some of my insights as to how to play Jarvan IV based on my personal experience. As a glimpse to my skill with Jarvan IV, while I seldom play ranked games (though I'm currently operating at a 2:1 win to loss ratio), I typically have a kill to death ratio of about 2:1 in normal games, though better and worse ratios do occur from time to time, as everybody has their good and bad games.

Edit (9/13/2011) - I've decided to clean this guide up a bit and update it to better reflect my thoughts on how to build Jarvan IV.

Pros

• Can jungle while fulfilling the role of tank via initiation.
• If focused, harder to kill than carries.
• If not focused, can still output a large amount of damage.
• A bigger asset to the team than full out tank Jarvan IV based on my experience.

Cons

• Not as durable as a pure tank.
• Low mana cripples your ability to jungle at the beginning, so blue buff is advisable.
• Blue Golem at level 1 with no leash is possible, but leaves you at very low health and susceptible to ganks.
  

Greater Mark of Desolation x 9 - I believe that armor penetration marks are the best for maximizing physical damage.

Greater Seal of Armor x 9 - Flat armor seals are extremely beneficial to jungling as they reduce the amount of damage you take from creeps and can be the difference between keeping life and death.

Greater Glyph of Scaling Magic Resist x 9

Greater Quintessence of Desolation x 3 - Same logic behind marks.

Ideal Items

Mercury's Treads - Mercury's Treads are easily the best boots for Jarvan IV, as they give 25 magic resistance and 35 tenacity. Since boots are a sunk cost in terms of item slots, it's typically ideal to get Mercury's Treads for the 35 tenacity alone, as it will allow you to use another slot that would otherwise be used on a tenacity item. However, if the enemy team has a substantial amount of physical damage, it would be advisable to get Ninja Tabi instead.

Trinity Force - A Trinity Force has a lot of stats that are of use to Jarvan IV including a chance to slow enemies and increased movement speed, allowing you to catch up with enemies and keep them within your grasp, all for the price of one item slot.

Banshee's Veil - With health, mana, and magic resistance, a Banshee's Veil helps out in terms of survivability and sustainability. However, the real value of a Banshee's Veil is in the spell shield, which can prevent disables or massive nukes from striking you, making it an item worthy of almost if not every champion.

Sunfire Aegis - I choose to get a Sunfire Aegis because I feel that a character fulfilling the role of tank must at least have 3000 health. The reason why I get a Sunfire Aegis instead of a Warmog's Armor is that in addition to health, it offers armor and a bit of extra damage output.

Atma's Impaler - With over 3000 health at level 18, Atma's Impaler Gives around 60 Damage in addition to % critical chance and armor, making it a valuable item in terms of balancing survivability and damage output.

Infinity Edge - While Infinity Edge may be a bit sacrificial to survivability, with Trinity Force and Atma's Impaler there is a significant chance to crit, meaning that the extra crit damage on Infinity Edge should be extremely beneficial to damage output.


An Alternative Build - For heavy magic damage teams

Frozen Mallet & Force of Nature - For heavy magic damage teams, I would recommend the combination of both of these items. However, the downside of this combination is that it takes up two item slots instead of one if you view it as getting both the slow and increased movement speed of Trinity Force.

Youmuu's Ghostblade - Youmuu's Ghostblade, in addition to the increased damage output it provides, actually has a fair amount of synergy with Dragon Strike, due to armor reduction mechanics being applied before armor penetration. The reason that it is not chosen in a normal build is the need for a Sunfire Aegis to break 3000 health.

Mercury's Treads

Infinity Edge

Banshee's Veil


As you may see, Wriggle's Lantern is included in both item sequences, but is not included in both lists. This is because I buy a Wriggle's Lantern to help with jungling, but fully intend to sell it when I have sufficient gold to buy an Infinity Edge as my last item, despite games rarely lasting long enough for me to consider selling it.

Also, once every item is purchased, make sure to spend your excess gold on buying elixirs.

Demacian Standard should be maxed first, as the increase to attack speed and armor greatly help out in the jungle. When combined with Dragon Strike, it causes every enemy between you and your standard to be knocked up. I have a few notes as to how to properly use this combo.

• By mastering the quick followup of Dragon Strike after Demacian Standard, you can often be too fast for an enemy to flash away.
  
• By using your ward from Wriggle's Lantern or Demacian Standard for sight, it is possible to use your combo and smite to steal Dragon or Baron Nashor for your team and then flash over the wall to safety.
  
• The combo should sometimes be saved to interrupt channeled spells such as Warwick's Infinite Duress, Malzahar's Nether Grasp, Katarina's Death Lotus and Fiddlesticks's Bountiful Harvest.

My advice to using Golden Aegis is to use it to slow enemies you are ganking and to be ready to use it for incoming damage such as Karthus's Requiem. I do not consider the shield and AoE slow incentives of Golden Aegis to consider leveling it over Dragon Strike.

I have three pieces of advice as to how to properly use Cataclysm.

• You absolutely cannot afford to trap a helpless ally inside of Cataclysm.
  
• Since many players choose Flash as a Summoner Spell, it can be difficult to gank even with Cataclysm. My advice is to try to scare a player into using Flash by initiating upon them with your combo and then once they use Flash use Cataclysm. This works because Cataclysm has a longer range than Flash. In case of Ezreal, Kassadin or other champions with a blink ability and Flash, you should save your combo or Flash for their first attempt to escape and your Cataclysm for their second attempt to escape.
  
• If possible, you should save your allies from enemies in pursuit by locking the enemies within Cataclysm and then using your combo or flash to escape without dieing.

Smite - Necessary for jungling.

Flash - In addition previously mentioned synergy with your abilities, Flash provides for easier ganks and escapes.

Items - Start off with a Cloth Armor and Health Potion x 5. Try to use a Health Potion immediately after the previous one wears off, but make sure there is at least one Health Potion left over after your first jungle rotation and that you do not consume a Health Potion if you are not missing enough life to make it an efficient use.

1. Ancient Golem (aka Blue Buff) & Young Lizard x 2 - Ancient Golem as a starting point is ideal, as the mana cost of your abilities can end up crippling your early game jungle. It is however difficult to kill Ancient Golem without a leash, so you should ask for a leash (if not a bit of help in killing it) and also a lookout in case the enemy team tries to counter you. Be particularly careful if the enemy team has a Clairvoyance, a Stealth Champion, or no Jungler, as these factors particularly increase the likelihood that you will be ganked. Ideally you should use Demacian Standard once the minions start attacking you and use Smite when the ancient golem has about 500 health left. This should help to maximize the damage your Martial Credence does.
   
2. Giant Wolf & Wolf x 2 - Use Demacian Standard and Dragon Strike. Kill the Giant Wolf first.
   
3. Wraith & Lesser Wraith x 3 - Be cautious when heading to the Wraith Camp if the enemy team has a Shaco on their team, as Shaco players sometimes try to lay several Jack in the Boxes in the bush outside of the Wraith Camp to try and steal a first blood. Walk around the bush if necessary and/or move on. Use Demacian Standard and Dragon Strike. Kill the Wraith first.
   
4. Golem x 2 - Use Demacian Standard and Dragon Strike. Use Smite on the first golem you target when it has about 500 health left.
   
5. Recall Back to Base - Once you kill Golem x 2, you may want to look for someone to gank. Be cautious though, as without using your final Health Potion and subsequently slowing your jungle rotation or gold flow by buying another, you will be low on health. Buy a Long Sword once back at base.
   
6. Wolves - Repeat step two.
   
7. Wraiths - Repeat step three.
   
8. Elder Lizard (aka Red Buff) and Young Lizard x 2 - About now your blue buff will wear off. Use all of your abilities (including Smite as late as it remains efficient to do so]] to kill the Elder Lizard first and use your final Health Potion.
   
9. Golem x 2 - Repeat step four.

After this, you are free to kill your jungle again as it re-spawns or gank. I would suggest waiting till level 9 with a Wriggle's Lantern before trying to solo Dragon. Be cautious however, as the enemy team may have Dragon warded.

Make sure to use your Wriggle's Lantern ward at key points, such as Dragon and Baron. If you are particularly good at surviving and you know that the enemy team is making good use of wards, do not be afraid to buy an Oracle's Elixir. Each ward cost the enemy team 75 gold and awards 25 gold to the person who kills the ward, such that it only takes 4 wards being destroyed to make Oracle's Elixir worth it.

Well, I can't think of anything else, so I hope you find this guide useful. Thank you for viewing it, unless you're a troll, in which case **** you.