Ymir the Frost Giant

The goal of this build is simple, to be as tanky as possible, without losing on power at the same time. It will also show how to be a good support with this build as well.

I will go over each and every item pick for Ymir, to guide as I best see fit.

When going into an Arena Queue, it is important to note that you will have no need for potions, since you are close to your fountain. After buying Magic Shoes, you should go one of three above mentioned relics, depending on the situation:

Sanctuary - Not recommended in most cases, but if you find that enemies will burst you down in the beggining, you can take this.

Meditation - This should be your main pick, as you will be able to get out of critical situations with it, and also help someone get out of the same situation if needed. This is the first item to become a little more supportish.

Purification - Take that if enemy team has way more crowd control(CC) than you can remove with your ult. So if enemy team's only CC is Ares Ultimate, you are safe, because your ultimate works as a purify as well.

In other modes, Ymir has little to no use in Sanctuary for the team. That is the reason why Meditation should be your #1 pick on those modes. Also, you should start with Magic Shoes and 4 of each pots to help you survive in lane atleast until level 5, where you get your ult.

This way of starting is supposed to make you appear in lane constantly, without backing, eventually getting a small advantage if you force enemies back to base.

Buy wards if you need more lane control.

This part of the build is supposed to be finished a little after you get your second relic, at level 12.

After finishing on Shoes of the Magi, you are supposed to go onto Bulwark of Hope, so you can't be taken down easy, especially because of its passive.

When Bulwark of Hope is bought, you should make a decision between Obsidian Shard and Bancroft's Talon:
Obsidian shard - When targets are a little tankier than expected, and you can't get enough penetration from Shoes of the Magi.
Bancroft's Talon - When targets are squishy, and you need to deal as much as damage possible, without destroying any of their remaining protections.

After building either Obsidian Shard or Bancroft's Talon, you should make another decision, this time around your team:
Sovereignity - When enemy team is composed of mostly physical targets who are ahead.
Hearthward Amulet - When enemy team is composed of mostly magical targets who are ahead.

Your relic should be taken depending on the situation:
Meditation - If your first relic was Purification or Sanctuary
Blink - For suprising enemies with no escape
Thorns - To help you escape or initiate with bursty enemies
Shell - For teamfights where your team needs more protections and damage reductions.
Curse - If enemies have healers that give them too much sustain

In case of healers with too much sustain, you should take Divine Ruin instead of Obsidian Shard and Bancroft's Talon.

When finishing the build, you should take Etheral Staff as item #5 because it will enable you to get more HP and convert all that HP that you got before into more and more power.

After that, you are presented with one more choice:
Rod of Tahuti - When you need as much as power as possible
Polynomicon - Strongly recommended. When you deal enough damage, use this to remove enemies with your basic attacks, especially good because of your passive proc.
Spear of Desolation - When you need both damage and a little bit of penetration, against defensive targets.

At this point, the build is pretty much finished, you should be focusin on potions and elixirs now, giving priority depending on if you need more defense or damage.

P. Frostbite - When Ymir hits enemies with damaging abilites, they get an effect called "Frostbite" that makes them deal 10% less damage, and makes Ymir's basic attacks deal 100% more damage.

1. Ice Wall - Good to get, but not to max until no other choice is left. Provides enough lane control

2. Glacial Strike - Should be prioritised when leveling your abilities, has huge damage that is easy to confirm

3. Frost Breath - Should be leveled when Spikes and Ultimate are not avilable to level, provides a decent amount of CC

4. Shards of Ice - Level when it is avilable to be leveled, has huge damage that is very easy to hit. But beware, if you are killed while charging it, you will reset it and deal no damage.

Starting the fight:
When a fight is about to pop, your best way of using your abilities is:
3>2>1>Basic Attack
That way you are supposed to freeze enemies, throw your spikes, and block any of their attempts to escape with your wall.

If you bought Polynomicon, you can follow the next order to get maximum damage out of it:
3>Basic Attack>2>Basic Attack>1>Basic Attack
This could take some time to get used to, but with it you can proc Polynomicon 3 times, which will often be more than enough to kill squishy targets.

If you have your ultimate ready, you can go with alternate combo that will enable you to kill each squishy target without sanctuary (Just don't forget to let that ultimate charge to max and not to engage with little HP):
3>1>4>2>Basic Attack
This way you can freeze them and block their escape with your wall, then ult to get the maximum damage. After that, finish them if needed with your 2 or Basic Attack.

If combos are properly used, with a little team help, you can take down targets very easy.

Ymir is one of the best supports, having great pros, and some cons. Here are some of mine that I could think of:

Pros:
-Huge Area Damage
-Huge Survivability
-Good CC
-Lane control and wave clear

Cons:
-No escape
-If out of position, easy to take down
-Useless if he falls behind

Overall, Ymir can be one of the best players in the Match if built and played correctly, but can be worse if he isn't played right.

Here are few tips to be better:
-Buy wards and use them
-If you get Polynomicon, hit one basic attack after each ability, including your wall.
-Know when to retreat, don't engage with little HP
-Save your teammates, take some shots from enemies for them and don't be afraid to Meditate them when they are in need
-Keep an eye on your Bulwark of Hope passive timer, it can be very life saving
-Do not go into fights where you are the only one able to attack, or where you are tactically outnumbered
-Play calm, when you are in stressful situations, just focus as much as you can

Hope you liked my build, Ymir says HI!