According to what most people that opened a lot of packs said, there's quite a low chance of getting a legendary.
On average, people get 1 legendary per 20-25 packs. Some are less fortunate than that however.
Source: S1, S2, S3
This is according to my own experience. I have 257 arena wins and I like to keep stats. I searched previously but couldn't find an official source for this.
1st, 10th, 20th, 30th pick in Arena are always rare or higher: I call this Rare Turn, the others are normal turns.
At any normal turn, you can get one of these sets:
- 3 free
- 2 free 1 common
- 1 free 2 common
- (possibly 3 common as well didn't pay attention, can't verify this)
- 1 Rare turn ( % not sure I would guess about 5% - 10%)
In a normal turn roughly you have a 60% chance of getting a free and 40% chance of getting a common card.
At any rare turn, you can get one of these sets:
- 3 rare
- 3 epic
- 3 legendary
I got a legendary about every 10 games and since we have 4 rare+ picks I assume the chance of getting a legendary in a single rare turn is about 2%
I got an epic about every game so I assume the percentage for that is about 20%
TL;DR:
Normal Turn:
Rare Turn:
- Rare+ : 4 times
- Epic : 20%
- Legendary : 2%
I don't have a source for this its all according to my personal experience. These numbers are most likely wrong, but should give the general idea. More data is needed for better estimates.
In a normal arena deck you will have something like this:
- 15 Free
- 10 Common
- 4 Rare
- 1 Epic/Legendary
Of course if you are lucky you could get 4 legendaries, 10 rares, etc..
Best Answer
One C'thun and two Beckoner of Evil cards are rewarded after you acquire at least one pack of Whispers of the Old Gods and enter the "Open Packs" screen.
This will remain in place for as long as Whispers of the Old Gods packs are available, presumably, since the stated reason for the promotion is so players can use all the common and rare C'thun synergy cards in the set without having to worry about spending dust or money to get the centerpiece. In addition, the normal versions of these cards are presently uncraftable.
During the launch window of Whispers of the Old Gods, logging in will reward you three free packs of the set, so you will not need to spend any money or in-game gold to get C'thun if you take advantage of the launch promotion. This began on the Whispers of the Old Gods launch date, and the packs are awarded when you log in to the game. An end date has not yet been announced.
Both of these promotions were revealed at the Whispers of the Old Gods announcement press event, according to BlizzPro.
During the Hearthstone live-stream on April 21st, two more promotions were announced:
These promotions show up as "Legendary Quests" in your quest log. If you already had three active daily quests, they replace the quest on which you had the least progress, or the least valuable quest if you had no progress on any of them.