Yes, this is a thing. If you play Udyr, you don't have to go phoenix. Crazy, right? Well, then why would you take tiger over phoenix? Hmm... well, when was the last time you saw a Tiger Udyr? You probably can't remember. This is because he is very underestimated. He is very powerful, and when you end up 10/0 at 20 minutes with your enemies baffled at your power, you'll just laugh at them and then backdoor their nexus ;)

-CSing is so easy, it feels like cheating
-Excellent trading, especially early
-Most people underestimate you in lane at first, use this to your advantage
-Great sustain with turtle stance's free lifesteal
-Excellent splitpusher
-Great Roamer
-Excellent dueling
-Mana Problems without proper management
-Can be poked extremely easily without retaliation
-Greedy playstyle to be successful

Marks
-Flat AD: Tidyr benefits greatly from flat AD, so we gave him some of these marks.
-Attack Speed: Tidyr also needs a bit of attack speed to get his tiger enhanced AA's, so throw some attack speed marks in there
Seals
-Flat Armour: I feel that these are the only good marks on Udyr. If you have any suggestions, please put them in the comments.
Glyphs
-Flat MR: These are to get you through lane. Nothing else.
-Flat CDR: CDR is AMAZING on Udyr, but we're going to be building a lot, so scaling CDR won't be as beneficial to us as flat for the early game.
Quintessences
-Flat AD: Same as marks. Flat AD for more damage.

We take a 21/9/0 page because our friend Tidyr over here isn't a tank, nor is he a support.
Offense
- Sorcery: Delicious CDR that we love.
- Butcher /Feast: Farm, farm, farm!
- Brute Force : More AD...
- Martial Mastery : Even more AD!
- Executioner : For picking up them kills and trading in lane.
- Dangerous Game : Get in, get kills, and get out. Now with more safety!
- Warlord : AD!!! SO MUCH AD!!!
- Devastating Strikes : Getting through that nasty armour they all have. Great against tanks.
- Havoc : Because who doesn't like more damage?

Defense
- Block : So you can shrug off a bit more damage from the enemy's auto-attacks.
- Unyielding : 2 less damage from all champions? Why not?
- Recovery : A little regen never hurt.
- Veteran's Scars : How scars help this much (or at all) is beyond me, but they've saved me countless times.
- Juggernaut : We do build a bit of health, so this gives us a little reward for getting some.

Bridge Between (Passive)
This is a cool passive that makes Udyr fast [in more ways than one ;) ] when changing stances.
Passive: When a new stance is entered, Udyr gains 10% attack speed and 5 movement speed for 5 seconds. This effect can stack up to 3 times.
This is a cool little bonus for whenever you switch stances. This synergizes very well with your Wilding Claw to give a huge attack speed steroid.

Wilding Claw (Q)
This is what makes Tidyr... well, Tidyr! This is your key to trading, farming, splitpushing... pretty much everything. But what does it do?
Upon activation, Udyr gains a 30 to 70% attack speed steroid for 5 seconds, and his first auto-attack after activation applies a DoT effect that deals 30/80/130/180/230 plus 1.2/1.3/1.4/1.5/1.6 physical damage that scales with your AD.
Persistent Effect: All auto-attacks while in Wilding Claw deal 0.15 bonus physical damage which scales with your AD.
Ok, so that's what it does, but how do I use it? Well, at the start of the game, before you leave your fountain and go to lane, throw your tiger stance on. This is so that if anyone sees you, they know that you are playing Tidyr, and it will confuse them. But in all seriousness, this is so when the first minions get to lane you can put a DoT on one without using any mana (Pro Tips! xP) For the majority of lane you want to be in Wilding Claw because it allows you to cs very easily.

Iron Mantle (W)
This is your shield from harass, your savior after a tower dive, your sustain in lane.
Upon activation, Udyr gains a shield that blocks 60/100/140/180/220 plus [0.5] damage, which scales with your AP.
Persistent Effect: Gain 10/12/14/16/18% life steal.
This is an amazing skill. Not only does it give you an awesome shield, but an AMAZING life steal bonus! Throw turtle on to block some harass, after you tower dive to tank the last shot from the turret as you run off into their jungle and recall. Also use turtle to recover from a trade. With this you have great sustain: so use it!

Blazing Stampede (E)
This is what you use when you "gotta go fast!" and then stun the enemy. Follow this up with Wilding Claw's DoT to get some HUGE damage off.
Upon Activation, Udyr gains a 15/20/25/30/35% movement speed bonus and he ignores unit collision for 2/2.25/2.5/2.75/3 seconds.
Persistent Effect: Auto-attacks stun the target for 1 second. The same target cannot be stunned more than once per 5 seconds.
This is a great skill for chasing, make sure to spam it when you're on someone's tail. It is also your best engage tool for a team-fight or and all-in. IF you're chasing someone, when you stun them, WALK AROUND THEM and INTO THE PATH THEY WERE TAKING. This allows you to get more auto-attacks off after their stun ends. After the stun ends and they start running again, RUN WITH THEM. This is key. Auto attack along the way, but don't fall behind. Your attack speed comes in handy here.

Wingborne Storm (R, but most certainly not an ultimate)
This thing... ew. For Tidyr, this is just disgusting. We take our last 3 points into this, but only because we have to. But even though we don't like to take this, it does help us push minion waves with its AOE damage.
Upon (a regretful) activation, Udyr emits pulsing waves of fire (kind of like a sunfire cape) that deal 15/25/35/45/55 plus [0.25] magic damage that scales with your AP each second to nearby enemies for 5 seconds.
Persistent Effect: Emits a short ranged AOE damage flame in front of Udyr every 3rd auto-attack, dealing 40/80/120/160/200 plus [0.45] magic damage that scales with your AP.
This skill... I just don't like it. That's why I play Tidyr. But basically, you can use this to clear large minion waves late game with the flame. I guess...

Starting Items
This is for those great lanes that you can roll all over. Also for AP lanes, such as Lissandra and
Ryze.
This is for those tricky lanes that'll have you spamming Iron Mantle half the time. The safer start, and actually my preferred start, due to Udyr's weak-ish first few levels.
A MUST for all laners, at least at first. A free ward at the beginning of the game, or rather, any point of the game, is invaluable. Always pick this up. You may swap it out occasionally for Sweeping Lens later.
Early Game
Again? Yes, again. It bay be beneficial to pick another one of these up, or, if you started Cloth Armor you may want to pick this up as well.
I personally love these. They significantly lower the damage output from the ADC to you, and they also lower the AA damage of any other AA based champion. We don't need the extra movement speed from Mobility Boots, we can just spam bear stance if we please. We also don't need the tenacity from Mercury's Treads because we are getting a Zephyr.
Ooh, marvelous Sheen. This item is amazing on Udyr. It synergizes so well with his kit it seems like cheating. If you switch stances ever few seconds you will continuously proc this thing. Amazing for splitpushing as well.
Just the next part of your Trinity Force that you should build.
Mid Game Core
This bad boy... It's amazing. It gives you spellblade, rage, movement speed, health, mana, AD, AP, even crit chance! Trinity Force has it all. This is just one of the few items to making you an absolute beast. (Or 4, for that matter.)
I like getting homeguard early, because it lets me back more without much punishment. Also allows for some epic homeguard + tp + bear stance ganks. :)
This thing is great. I just love it. AD, attack speed, a bit of CDR, and a movement speed buff. Oh, and to top it all off, we have 35% tenacity. That's the amount that you get from Mercury's Treads, and with these stats, it's no wonder we get Ninja Tabi.
If one or two of your teammates already has a Sweeping Lens pick this up. Two free wards is amazing, especially for splitpushing.
This is a great trinket if you swapped to Sweeping Lens earlier and you are teamfighting instead of splitpushing. Great for denying vision, especially around objectives. Also gives true sight, which is good against stealthed champions or when looking for Teemo shrooms or Shaco boxes.
Late Game
This is for splitpushing. Use it to disable towers when taking them without minions. Makes inner and outer turrets a joke. Also gives a cool passive for when near a turret (friendly's or enemy's, dead or alive) that gives movement speed.
We all mess up sometimes. Maybe it was that full-AP Ashe's cross-map arrow that stunned you under an inhibitor turret. Maybe you got screwed over by a roaming Baron . Whatever the case may be, Guardian Angel gives you another chance. Never a bad choice as the stats are solid.
Great pick. Completely counters attack speed champions via the aura and 100 armor. and on top of that, it gives 20% CDR. Oh, AND it gives 400 mana. 400! That's about 11 bear stances! A great item overall.
This item is like the new Randuin's Omen. It gives a great chunk of health and mana, some health regen, and an active that was made for initiating. A MUST for the teamfight build.
I usually don't get any raw magic resist items on Udyr, but if I am getting one, it's this. A good bit of health and the passive that increases healing on yourself, which applies to your Iron Mantle's passive life steal. I usually pick up Guardian Angel if I need MR, but if I was facing a full AP team, I would get this.
Elixirs
My most purchased elixir on Udyr. By far my favorite, because it allows you to absolutely melt turrets. Makes backdooring a breeze.
This is what I get if I know im about to take baron or do a game-changing teamfight. That little bit of extra AD just might do the trick. Also the healing is a nice bonus. My main elixir for teamfighting.
Another option, but my least used on Udyr This is for if you are the only initiator or if you need to just tank the enemy's CC. An ok choice for a tankier play style.

For my good ol' Summoner Spells, I like to take Teleport and Flash. Some alternatives would be Ghost, Ignite, Heal, Barrier, and Exhaust.
Primary Spells
Teleport is my favorite primary spell, for it allows you to have global map pressure. Also, it allows you to splitpush without worrying that you wont be there to take another objective like baron or miss a big team-fight. This also allows you to get back to lane fast in the earliest stages of the game.

Ignite is a very aggressive choice. Take it if you want to have a high kill pressure in lane, or if you want to all-in early. I don't really like this, but you can take it.

This is a very 'eh' choice. An emergency heal is nice, but that's why you have Iron Mantle. I suppose you could use it during a gank to heal your jungler during a gank for the health and speed boost, but it's not recommended.

The same as Heal. Don't take this. You don't need Barrier, because you have Iron Mantle. But I suppose, if you REALLY wanted to take it, it wouldn't kill you...

This is an ok choice. Exhaust should only be taken if you are super scared of your enemy laner. It isn't a bad pick though, especially against speedy enemies like Rammus and Hecarim, or AA reliant enemies, such as Tryndamere or Master Yi. Not a bad choice.

Secondary Spells
This should be your go-to secondary spell. It is so diverse, it's no wonder everyone uses it. Whether you chase, escape, juke, or steal with it, it doesn't matter. The most diverse spell, take it in almost any situation. (A cool thing you can do is a flash bear stance to lock down your opponent so your friends can catch up)

Ghost isn't a bad choice either. It's actually the better choice for chasing, as it gives a consistent movement speed boost over a long period of time. Also nice as it allows you to ignore unit collision. A strong choice, right up there with Flash. You really can't go wrong with either, so take your favorite. If you haven't played with Ghost for a while though, I encourage you to at least try it again with Udyr. It is solid on him, so at least give it a try.

Thank you so much for reading my guide on Udyr! Or should I say, Tidyr? Anyways, thank you for reading, I hope I helped somebody out, and hey, maybe I taught you a thing or two about our good ol' buddy, the Dyr. I am fairly new at making these guides, so all constructive criticism is appreciated. Got any recommendations, fixes, or additions to this guide? Put them in the Comments section, and I'll try to get back to you as soon as I can. That's all I got for today. And remember kids: DON'T EVER.... EVER.... use phoenix stance. (Unless you're playing phoenix Udyr, in which case, go for it.)

To Do List
-Add Jungle Build + Guide (Warrior and/or Devourer)
-Add Alterative Runes/Masteries/Item Builds
-Add More Things to Add
-Add Some Things That I Have to Add