Dragons have 2 breeding attempts by default. Each breeding uses one of breeding attempts. Demodragons don't spend any of their breeding attempts.
You can refill the dragon's breeding attempt by feeding other dragons to it. You cannot use demodragons to feed others.
Each player has only 1 breeding slot.
chances of giving rarity to descendants 
Attention! Fractional weights are used only to
calculate average weight of parents' rarity levels.


weight  save  raise  lower  
common

1  95%  5%  0%  
1.5  85%  15%  0%  
uncommon

2  65%  12%  23%  
2.5  65%  18%  17%  
rare

3  45%  9%  46%  
3.5  45%  14%  42%  
epic  4  30%  6%  64%  
4.5  30%  9%  61%  
legendary  5  10%  0%  90% 
Before the start of the breeding process, parents' average rarity level is calculated according the formula.
For example, parent1 is epic, parent2 is rare. Their average rarity is estimated as (4 + 3) / 2 = 3.5. According to this weight the chances are used in the calculations.
Passing sets to descendants
For each part of descendant's body a chances of getting each set are calculated. The chance is higher for the sets of parts of body that parents have.
Chance of getting a set, if parents have different sets 

Set of parent1  Set of parent2  Other sets 
48%  48%  1% 
Chance of getting a set, if parents have same set. 

Set of parents 1 & 2  Other sets 
95% / 60%  1% / 8% 
If there are less then 4 parts of body of the same set, the chances of getting sets are estimated as 95% and 1%. If there are four or more parts of body of the same set, the chances are 60% and 8%. For two fullset dragons, chances of getting fullset dragon is 0%.
In other words, if parent1's head is from set1, and head of parent2's head is from set 3, then there is 48% chance for descendant to get head from set1, 48% chance to get head from set 3, and 1% for each head from sets2, 4, 5 and 6.
If the same bodypart of both parents is from the same set, then there is 95% chance to pass it to new dragon, and 1% chance for any other set to pass to the new dragon.
Set calculation example for each part of body  
dragon 1  dragon 2  dragon 3  
# of set  #of set  # of set 
calculation of a part of body:


Head  1 
+

1 
=

1  95% chance for set1, 1% for any other set. Result  set1. 
Breath  2  2  3  95% chance for set2, 1% for any other set. Result  set3 

Element  1  2  2  48% chance for set1 and set2, 1% chance for any other set. Result  set2 

Wings  1  2  4  48% chance for set1 and set2, 1% chance for any other set. Result  set4 

Paws  3  4  3  48% chance for set3 and set4, 1% chance for any other set. Result  set3 

Tail  5  5  5  95% chance for set5, 1% chance for any other set. Result  set5 
Estimated breeding time for one parent 

rarity  days 
common  0 
uncommon  1 
rare  2 
epic  4 
legendary  8 
Estimated breeding time for one parent is calculated as time of breeding (according the table above) +time of breeding according to attack (1 point of DMG = 1 minute) for each parent + 5 minutes.
breeding time = RARITY_D1 + RARITY_D2 + ATTACK_MOD_D1 + ATTACK_MOD_D2 + 5 minutes.
Attention! If attack == 100, then time for attack mod is not added. This way, demo dragons and any base dragons have their breeding time estimated as 5 minutes.
Dragon's breeding attempts are estimated in a percentage. 50% equals to one breeding attempt. 100% equals to two breeding attempts.
The percentage that is refilled during the feeding depends on dragon's prices. For example, the dragon that is fed costs 75, and the dragon that is being fed to the first costs 20. In this case, it will refill 100 * 20 / 75 = 26.6667%.
You cannot feed rarer dragons to more common dragons.
1 minute of breeding timer skip= 1 mana potion.
First 6 breeding timer skips are free for new players.
Recovery after breeding:
Parents have to take a rest for a time that is triple the time of breeding.
To skip the recovery timer costs for 1 mana potion for 1 minute.
Price of the dragon depends on the price of his set on the market (it can vary depending on the demand of this set on the market), rarity, and breeding attempts.
rarity and coeficient of price  
rarity  coeficient 
common  1 
uncommon  10 
rare  30 
epic  60 
legendary  120 
breeding attempts and coeficient of price  
breeding attempt  coeficient 
0  50% 
1  75% 
2  100% 
PRICE OF DRAGON = PRICE_FOR_SET* RARITY_COEFICIENT* BREEDING_ATTEMPT_COEFICIENT