EDIT: 3/13/17 - Entered in new info on obtaining Mythic Cards and Glory cost for bundles in stores.
EDIT: 4/15/17 - Thank you and Credit to Throni360, for letting me know how to get Guild Keys.
EDIT: 7/27/19 - Edited info on Mythic Cards, how to obtain them, and ways to level/upgrade cards in general. Also broke the guide up into sections.
I do apologize in advance for this being a bit lengthy, but I wanted to give as much info as possible to try and make your journey to get this a little easier.
This achievement is for upgrading one of your Troops to Level 20.****Only Mythic Class cards can get to Level 20****
Mythic is the highest class a card can be, the card classes are:
-Common - card is white in color
-Rare - card is green in color
-Ultra Rare - card is blue in color
-Epic - card is purple in color
-Legendary - card is orange/gold in color
-Mythic - card is teal in color (I think its supposed to be crystal, but it looks like teal)The Easy Part
Simply go into your Troops menu, select a Mythic Class card, hit Y for the Crafting menu and then use Souls to level up the card to 20 and your achievement should unlock.
Depending on what level that card already is when you upgrade it will depend on how many Souls you need to spend. But upgrading a Level 1 card to a Level 20 card will require you to spend about 7000 Souls.
Or you can use Orbs of Growth. A Normal Orb of growth will raise the card 1 level and a Major Orb of Growth will raise the card to it's max possible level.The Hard Part
- Getting a Mythic Class card
Either: A) Get one of Mythic class troops available in the game or B) Ascend a lower class troop to Mythic. Getting one of the already Mythic class troops
As of the 7/1/19 Title Update 14 - Patch 4.4, there are 43 Mythic Class cards in the game. You can see them in the Troops menu if you use the filters to Show All cards and then sort by Base Rarity, so getting one of them and leveling the card is all you would need to do.
There are currently 3 ways to get one of the 43 Mythic Class cards.
1) You can craft one of them in the Soul Forge (found under the Games menu).
-What ones are available to craft is random and changes on a weekly basis.
-They also require 4000 Diamonds (obtain from Dungeon Battles under the Games menu or from crafting them in the Soul Forge), 10 Celestial Traitstones, and 20,000 to 50,000 Souls.
-As far as I know there are 2 exceptions to this, with is Xathenos (which is required for another achievement) as he requires 3 weapons that you have to craft (all of which need jewels, gems, celestial traitstones, and 100,000 souls each) as well as Gems and Zuul'Goth, which requires Orbs of Power instead of Celestial Traitstones.
2) Get the Mythic Treasure card called Sacred Treasure from opening rifts in the Underworld at each of the Faction Kingdoms or during Faction Events.
-This requires Chaos Shards, which are obtained from Delves.
-Which cards you get from the rifts are random, but will be combination of the troop cards for that specific delve location and treasure cards.
-You are not guaranteed a treasure troop when spending Chaos Shards on rifts.
-During Faction Events you can spend Gems in the Faction Event Shop and you will get random treasure cards.
3) Open chests. Certain chest types have a chance to give you a Mythic Class card although those chances are very very low.
-Glory Chests - using either Glory or Glory Keys
-Gem Chests - using either Gems or Gem Keys
-VIP Chests - you need VIP Keys and this requires you to spend real money in the Shop to earn VIP Points.
--You need enough VIP points to get to Rank 5 in order to get a chance for a Mythic class troop, then you need to use VIP Keys, which are also bought with real money.
--Currently the only packs in the store that includes VIP Keys are the Typhoon of Keys pack for $100 (of the 450 keys in the pack only 15 are VIP), Mini VIP Pack for $5.00 (has 2 VIP Keys and limits 3 per player), the X-Ball Pet pack for $50 (includes 8 VIP Keys), and there is normally 1 pack in the Weekly store tab for $50 for a random troop based on the weekly event that also includes 5 Keys.
-Guild Chests - using Guild Seals (or by spending real money on Guild Keys through the Guild Menu).
--In order to get a chance for a Mythic Class card to appear in the Guild Chests, your guild will need a minimum of 10,000 seals earned in a week (if your guild has less than this, there is no chance to get one if you open the chests).
--The chance to get one becomes higher if your guild earns 20,000 and then 40,000 seals in a single week.
--Remember your total seals for the guild earned, resets each week. --A single person can only contribute a max of 1,500 seals a week to the Guild (unless you use an Orb of Clans to boost it by 300 or 1500).
--To get to 40,000 seals in a week, you would need at least 28 people in the guild all earning the max amount to give you the highest chance. Ascending a lower class card to Mythic
If you are unable to obtain one of the 43 Mythic Class cards, you can Ascend any of the other Troop cards up to Mythic class.
In order to Ascend a card from 1 class to another you need multiple copies of the card. For the first time ascending, you need 5 extra copies (so 6 copies in total) as you will sacrifice 5 to upgrade the 6th to ascend it to a higher class.
This is easiest done by ascending a Legendary class card to Mythic as you will only need 5 extra copies of that card.
But if you are starting with a much lower class of card the copies you need will double each time. So to upgrade a Common card (the lowest class), you will need to Ascend it 5 times, which will require you to have a total of 190 extra copies of the card.
As when ascending a card it takes:
5 extra copies for the first time
10 extra copies for the second time
25 extra copies for the third time
50 extra copies for the fourth time
100 extra copies for the fifth time
Once you do Ascend a card to Mythic you will unlock:
You can also Ascend cards by using Orbs of Ascension. A normal Orb of Ascension will raise the class of a card by 1 and a Major Orb of Ascension will raise a card directly to Mythic class regardless of it's starting class.
There is no easy way to get extra copies of a specific card as what chests give you are completely random. If you have the materials, you can craft multiples from what is available in the Soul Forge, but the requirements tend to be quite high. Easiest way to get extra copies of a specific card
While this is the easiest way, you do not get to pick the card, and it can be a bit of grind.
You will need to save up 12,300 Glory.
Glory can be obtained from basically everything in the game, though it's amount will vary.
-Daily Tributes, Log-In bonus (which is higher based on your PvP rank), from PvP, from using keys on chests, from Guild Tasks, Treasure Hunt mini game, and Delve rewards.
-Normal battles rarely give you Glory.
Then go into the the shop and look under the Glory Rewards tabs. Each week there is 1 Event pack for a specific Troop that you can buy with Glory for 300 Glory a piece. This is usually either a Common, Rare, or Ultra Rare Troop. And if it's Common or Rare, it normally gives you multiple copies of the troop, usually between 4-6 for a Common and 2-4 for a Rare. If it is an Ultra Rare troop, you will get 1.
When it is an Ultra Rare Class card (blue) you have to buy 41 of these packs since you need 40 extra copies of the card as you need to ascend the card 3 times. Which is why you need 12,300 glory (300 glory x 41 packs).
The packs also include specific traitstones, keys and gold, and sometimes those keys are Event keys. Now if there are Event Keys in these packs, you have a chance of getting another copy of the card in those packs from the Event Chests. So you may be able to save yourself from spending 12,300 Glory. But its best to have the total amount of Glory needed in case their are no Event Keys or you don't get extras from the Event Chests.
On occasion, the Troop in these packs is an Epic class (purple) and it will cost you 400 glory per pack and you get 1. In these cases, you only need about half the required glory as you only need to buy 16 packs, since you only need to Ascend it twice, at 400 glory each for a total of 6,400 glory.
Or if you don't mind spending actual money, under the Weekly Event Tab in the Shop, normally one of the $25+ bundles has a Troop card in it that gives you multiples of it, but its normally an Ultra Rare or Epic card. So you'd need to buy the bundle at least 3-4 times, unless you already had 1 or more the card. Or the $50+ bundles give you 1 Legendary card, so again you'd have to buy multiples. Misc Info about the Orbs
As I mentioned in the guide, Orbs can help speed up the leveling or raising the class of a specific card. There are 10 types of Orbs:
Orb of Chaos - randomly gives you one of the 9 other orbs.
Orb of Clans - gives you 300 Guild Seals
Major Orb of Clans - gives you 1500 Guild Seals
Orb of Growth - raises a troops level by 1
Major of Growth - raises a troops level to its maximum possible based on its current class.
Orb of Wisdom - unlocks 1 of the troops traits/skills
Major Orb of Wisdom - unlocks all 3 of the troops traits/skills
Orb of Ascension - raises the class of a troop by 1
Major Orb of Ascension - raises the class of a troop to Mythic
Orb of Power - is the combination of the Major Orbs of Growth, Wisdom, & Ascension.
In order to get any of the Orbs mentioned you will need to complete Events and win the rewards that offer the Orbs.
Events that have a chance to give you one of the Orbs are the Faction Event, Raid Boss, Siege Invasion, and Tower of Doom. Don't know if Guild Wars has Orbs as a reward because my current guild is inactive and hasn't participated in it in quite some time.
The Orb of Chaos will immediately give you one of the other orbs upon obtaining it. I have yet to receive an Orb of Power from them, so I do not know if it's possible for it to give you one.
You can craft the Major versions of Growth, Wisdom, and Ascension in the Soul Forge. They required 1000 Souls and 20 of the normal Orb versions to do so (which in my opinion kind of defeats their purpose and is a waste of 1000 souls).
You can craft Orbs of Power in the Soul Forge. Though crafting Orbs of Power is a waste in my opinion as they require 3 of each Major Orb version (except Clan) and 10,000 Souls to make 1 Orb of Power (so you basically trade enough Orbs to effectively max out 3 cards, to get 1 orb that does that). The only purpose I see to this is if you are trying to craft Zuul'Goth.
And that is all the info I currently have, I thank you for reading/skimming through it all.
If you have any questions, comments, or info to make this easier please let me know and I will modify the guide as needed. Also if you give negative feedback to the guide, please tell me why in the comments so that I can make changes in order to help you.