This is an off-tank Udyr build, as I found it the most useful way to play lane with Udyr. This is my first build so please leave constructive critisism.

Pros
+ Sustained damage troughout the whole game
+ Not squishy
+ Great built in escape
+ He's an animal master! Cons
- Can be nuked down quite easily when not fed enough
- Does not have any ranged skills
- Can be harrassed easily

Greater Mark Of Desolation: These are for that bit of armor penetration troughout the game, which can help you pick up that extra one or two kills.

Greater Seal of Armor: These are for an extra bit of sustain early-mid game. Because of this you might have those 20 hp left.

Greater Glyph of Magic Resist: These serve the same purpose as the seals, give you that extra bit of sustain throughout the game.

Greater Quintessence Of Desolation: These are for the more armored champions mid-late game, so that you do not need to build any then.

The masteries are focussed towards a more tanky and sustained champion. I go down the defensive tree and take the armor penetration in offense. This is a standard tank/offtank mastery.

I never really liked Doran's shield. For the spellcasters I nearly always use Doran's Ring and for carries Doran's Blade but even with tanks I went for the damage item, so the Doran's Blade. But after trying this on Udyr I finally understood why you should take this item. It gives very good early game sustain, armor, health and health regen. All these help you stay on lane longer and help you farm longer. Doran's Blade is also an option, but Udyr has great damage early game anyways.

The answer is dependable on your enemies. If they have a poor setup and play with 4/5 squishies, it's not as usefull as against a very tanky team. If the enemy team has that one unkillable Singed/ Rammus/etc. Go ahead and buy it. It also benefits against squishies, just not as much. And you will help your team a great deal.

This is not a common item for Udyr I believe. But if you are standing in the middle of four enemies, you will unnoticably be pumping out damage to them. I have caught champions with low-hp without being able to touch them because of Sunfire Aegis. It also gives health and armor on top of the amazing passive. Which helps with your tankyness.

Atma's Impaler is one of the best AD Tank items in the game. It stacks AD on your max health. This is amazing as we get ~55 AD at level 18 which is more then a B.F. Sword! On top of the armor and crit strike you get thats really nice!
- If you are playing against 3/4 AP champions, consider this instead of Madred's Bloodrazor as most AP champs are squishy.

- This is like the AD version of the Force of Nature it provides 100 armor and 30% returning damage. Great against e.g. Tryndamere/ Master Yi

- This is a generally a more tanky boots choice but doesn't provide the tenacity which is so valuable.

- This is a free third summoner spell. It's called Cleanse. It removes all debuffs. It's great against a CC dependant team or just when you don't feel comfortable about the CC they have.

Udyr doesn't have the standard 3 skills and an ultimate. He has 4 stances with entirely different purposes. I'll explain them briefly and try to learn the uses of each skill. His stances stack to his passive which I'll also explain.

Passive

Bridge Between

Udyr gains 10% attack speed per "stack". He gains a stack when Udyr enters a stance. The effect stays for 5 seconds. When he enters another stance within this time the bonus stacks. The stack limit is 3. This is quite useful when about to gank someone and you're not low on mana. Try to "Stance Dance" before getting to the brush of the lane to have those 2-3 stacks ready.

Q

Wilding Claw

This is your main damage output. It scales very good with your AD (x1.5) and will burn through HP like crazy. When activated, your attack speed increases by 15/10/25/30/35% on top of the passive 20/25/30/35/40%.

W

Iron Mantle

This is a part of your escape/survive abilities. It gives you a shield for 60/100/140/180/220 damage + (50% of AP) It is also useful when you are e. g. ignited and don't want to take too much damage. Pop on the Turtle Stance and the ignite destroys that instead of your valuable health.

E

Blazing Stampede

This is your main ganking/escaping skill. When activated is gives you a 15/18/21/24/27% movement speed boost for 2/2.5/3/3.5/4 seconds. The passive stuns enemies for 1 second. This can only occur once per 6 seconds.

R

Wingborne Storm

This is a skill I use barely if even at all. I just don't like it. Some people may swear to Phoenix Stance, I don't see the point. On activation it sends out pulsing waves of fire damaging enemies for 15/25/35/45/55 damage per second. Also, his AP is increased by 16/24/32/40/48 and your AD by half this amount. When activated, every 4th attack will engulf his target in flames dealing 40/80/120/160/200 + (50% of AP) magic damage.

I like Wilding Claw over Wingborne Storm so I max Wilding Claw first, Iron Mantle second and Blazing Stampede last. The ranks don't affect the stun time so I max it after turtle stance. When I really want to rush someone, I use Flash or Ghost. Iron Mantle is also a viable skill, as it saved me and will save you many times. About to die by Ignite? Pop Iron Mantle. Being chased by enemies with low-hp? Pop Iron Mantle and combine it with Blazing Stampede for a fast running tank. Max Wingborne Storm last as I don't build AP in this build.

Good Choices
+ Ghost (Nice for chasing/Escaping. Scales off in late game though.
+ Flash (Excellent, Chase Escape, this is such a usefull spell, even after the nerf.)
+ Ignite (Excellent finisher and can hurt champs with lifesteal very much.)
+ Exhaust (Nice for 1v1's chasing etc.)
+ Teleport (Only if solo top.)
+ Cleanse (Meh. Ok, but you have Mercury's Treads. if you have too much trouble buy Quicksilver Sash.)
Bad Choices
- Heal (Not as useful either especially late game.)
- Clarity (Udyr is not that mana hungry.)
- Clairvoyance (A support spell.)
- Promote (Not useful at all.)
- Surge (Not so useful on Udyr.)
- Revive (Your objective is not to die.)
- Smite (This is not a jungle build.)
- Garrison (This isn't dominion and this is a tank spell.)

What should your focus be early game?

Early game is ~levels 1-7. This is not always the same but it is the phase when everybody is on their own lane and ganks are rare. Udyr, like almost any champ should try to focus on
last-hitting the minions and harrassing his enemies. A great harrass combo is to run in with your E ( Blazing Stampede) And hit them 1-2 times with your Q ( Wilding Claw) This should deal a nice chunk of damage and they are not able to harrass back easily because of the stun.

What should your focus be mid game?

Mid game is ~levels 8-14. This changes per game but it will mostly be around these levels. During the mid game phase, you will gank and be ganked more often, junglers come into play more, and the first team-fights might emerge. Udyr is quite a good ganker, and you can gank other lanes if you feel confident you can get a kill/assist.
Caution!: Watch out for enemy crowd control because Udyr is vunerable to this, even though he has his merc threads.

What is your role late game?

Late game starts around ~levels 14+. Team-fights are a common sight, and because you are an
off-tank you are one of the first to go in, and one of the last to go out. This would seem like wasting your life. But because Udyr has great sustain, he can tank multiple enemies while dealing devastating damage himself. Because you probably are a high-value target the enemies will focus you, while your carries slay your enemies in the background. This doesn't mean you run in, deal damage and die, I survive ~80% of the teamfights, and most of the time even get some kills.

Overall, Udyr is a fun and good champion to play. He might be a bit tricky but you'll have fun when you understand him. He's a great champion and he can fulfill a lot of roles. Please vote and leave constructive critisism please! Hope you enjoyed and learned something!

~MrQzNinja

Update: 1.01 - Put early/mid/late game sections in. Put skill explanation in.
Update: 1.02 - Put in the wikicodes and some minor sentence changes.
Update: 1.03 - Re-Wrote Items section. Added situational items as well.
Update: 1.04 - Re-did the mastery tree, and refreshed the item build. I haven't tried Udyr top extensively, but it can work.