A random selection of 8 items are put on a wheel and spun.            
The reward given is the item that the wheel lands on.            
Below is a list of overall rewards and their probabilities:

Chance ChestMega Chance ChestGrand Chance Chest
You will receive 1 of the following:You will receive 1 of the following:You will receive 1 of the following:
ItemProbabilityItemProbabilityItemProbability
Bunny Dragon Whelp x 10.74%Bunny Dragon Whelp x 10.74%Bunny Dragon x 10.74%
Cat Dragon Whelp x 10.74%Cat Dragon Whelp x 10.74%Cat Dragon x 10.74%
Doll Dragon Whelp x 10.74%Doll Dragon Whelp x 10.74%Doll Dragon x 10.74%
Fay Dragon Whelp x 10.74%Fay Dragon Whelp x 10.74%Fay Dragon x 10.74%
Jungle Dragon Whelp x 10.74%Jungle Dragon Whelp x 10.74%Jungle Dragon x 10.74%
Turtle Dragon Whelp x 10.74%Turtle Dragon Whelp x 10.74%Turtle Dragon x 10.74%
Wood Dragon Whelp x 10.74%Wood Dragon Whelp x 10.74%Wood Dragon x 10.74%
Nilla Dragon Whelp x 10.74%Nilla Dragon Whelp x 10.74%Nilla Dragon x 10.74%
Passion Dragon Whelp x 10.74%Passion Dragon Whelp x 10.74%Passion Dragon x 10.74%
Diva Dragon Whelp x 10.74%Diva Dragon Whelp x 10.74%Diva Dragon x 10.74%
Samba Dragon Whelp x 10.74%Samba Dragon Whelp x 10.74%Samba Dragon x 10.74%
Moon Dragon Whelp x 10.74%Moon Dragon Whelp x 10.74%Moon Dragon x 10.74%
Sea Dragon Whelp x 10.74%Sea Dragon Whelp x 10.74%Sea Dragon x 10.74%
Anubis Dragon Whelp x 10.74%Anubis Dragon Whelp x 10.74%Anubis Dragon x 10.74%
Viking Dragon Whelp x 10.74%Viking Dragon Whelp x 10.74%Viking Dragon x 10.74%
Sensei Dragon Whelp x 10.74%Sensei Dragon Whelp x 10.74%Sensei Dragon x 10.74%
Zeus Dragon Whelp x 10.74%Zeus Dragon Whelp x 10.74%Zeus Dragon x 10.74%
Crimson Dragon Whelp x 12.27%Crimson Dragon Kid x 12.27%Crimson Dragon x 12.27%
Gargoyle Dragon Whelp x 12.27%Gargoyle Dragon Kid x 12.27%Vicious Gargoyle Dragon x 12.27%
Golem Dragon Whelp x 12.27%Golem Dragon Kid x 12.27%Golem Dragon x 12.27%
Grass Dragon Whelp x 12.27%Grass Dragon Kid x 12.27%Grass Dragon x 12.27%
Green Dragon Whelp x 12.27%Green Dragon Kid x 12.27%Green Dragon x 12.27%
Rock Dragon Whelp x 12.27%Rock Dragon Kid x 12.27%Rock Dragon x 12.27%
Roc Whelp x 12.27%Roc Kid x 12.27%Roc x 12.27%
Sharp Dragon Whelp x 12.27%Sharp Dragon Kid x 12.27%Vicious Sharp Dragon x 12.27%
Spotted Dragon Whelp x 12.27%Spotted Dragon Kid x 12.27%Spotted Dragon x 12.27%
Toadstool Dragon Whelp x 12.27%Toadstool Dragon Kid x 12.27%Toadstool Dragon x 12.27%
Nature Dragon Whelp x 12.27%Nature Dragon Kid x 12.27%Nature Dragon x 12.27%
Golden Duck Egg x 11.79%Midas Duck Birthling x 11.79%Young Midas Duck x 21.79%
Butterfly Dragon Egg x 11.79%Butterfly Dragon Whelp x 11.79%Butterfly Dragon Kid x 21.79%
Cosmos Dragon Egg x 11.79%Cosmos Dragon Whelp x 11.79%Cosmos Dragon Kid x 21.79%
Life Dragon Egg x 11.79%Life Dragon Whelp x 11.79%Life Dragon Kid x 21.79%
Pegasus Egg x 11.79%Pegasus Birthling x 11.79%Pegasus Kid x 21.79%
Tribal Dragon Egg x 11.79%Tribal Dragon Whelp x 11.79%Tribal Dragon Kid x 21.79%
Wise Dragon Egg x 11.79%Wise Dragon Whelp x 11.79%Wise Dragon Kid x 21.79%
Crimson Dragon Egg x 22.27%Nest of Crimson Dragon Eggs x 12.27%Crimson Dragon Kid x 21.14%
Gargoyle Dragon Egg x 22.27%Nest of Gargoyle Dragon Eggs x 12.27%Gargoyle Dragon Kid x 21.14%
Golem Dragon Egg x 22.27%Nest of Golem Dragon Eggs x 12.27%Golem Dragon Kid x 21.14%
Grass Dragon Egg x 22.27%Nest of Grass Dragon Eggs x 12.27%Grass Dragon Kid x 21.14%
Green Dragon Egg x 22.27%Nest of Green Dragon Eggs x 12.27%Green Dragon Kid x 21.14%
Rock Dragon Egg x 22.27%Nest of Rock Dragon Eggs x 12.27%Rock Dragon Kid x 21.14%
Roc Egg x 22.27%Nest of Roc Dragon Eggs x 12.27%Roc Kid x 21.14%
Sharp Dragon Egg x 22.27%Nest of Sharp Dragon Eggs x 12.27%Sharp Dragon Kid x 21.14%
Spotted Dragon Egg x 22.27%Nest of Spotted Dragon Eggs x 12.27%Spotted Dragon Kid x 21.14%
Toadstool Dragon Egg x 22.27%Nest of Toadstool Dragon Eggs x 12.27%Toadstool Dragon Kid x 21.14%
Nature Dragon Egg x 22.27%Nest of Nature Dragon Eggs x 12.27%Nature Dragon Kid x 21.14%
Midas Duck Birthling x 11.79%Young Midas Duck x 11.79%Midas Duck x 11.79%
Butterfly Dragon Whelp x 11.79%Butterfly Dragon Kid x 11.79%Butterfly Dragon x 11.79%
Cosmos Dragon Whelp x 11.79%Cosmos Dragon Kid x 11.79%Cosmos Dragon x 11.79%
Life Dragon Whelp x 11.79%Life Dragon Kid x 11.79%Life Dragon x 11.79%
Pegasus Birthling x 11.79%Pegasus Kid x 11.79%Pegasus x 11.79%
Tribal Dragon Whelp x 11.79%Tribal Dragon Kid x 11.79%Tribal Dragon x 11.79%
Wise Dragon Whelp x 11.79%Wise Dragon Kid x 11.79%Wise Dragon x 11.79%
Bunny Dragon Egg x 10.74%Nest of Bunny Dragon Eggs x 10.74%Bunny Dragon Kid x 20.74%
Cat Dragon Egg x 10.74%Nest of Cat Dragon Eggs x 10.74%Cat Dragon Kid x 20.74%
Doll Dragon Egg x 10.74%Nest of Doll Dragon Eggs x 10.74%Doll Dragon Kid x 20.74%
Fay Dragon Egg x 10.74%Nest of Fay Dragons x 10.74%Fay Dragon Kid x 20.74%
Jungle Dragon Egg x 10.74%Nest of Jungle Dragon Eggs x 10.74%Jungle Dragon Kid x 20.74%
Turtle Dragon Egg x 10.74%Nest of Turtle Dragon Eggs x 10.74%Turtle Dragon Kid x 20.74%
Wood Dragon Egg x 10.74%Nest of Wood Dragon Eggs x 10.74%Wood Dragon Kid x 20.74%
Nilla Dragon Egg x 10.74%Nest of Nilla Dragon Eggs x 10.74%Nilla Dragon Kid x 20.74%
Passion Dragon Egg x 10.74%Nest of Passion Dragon Eggs x 10.74%Passion Dragon Kid x 20.74%
Diva Dragon Egg x 10.74%Nest of Diva Dragon Eggs x 10.74%Diva Dragon Kid x 20.74%
Samba Dragon Egg x 10.74%Nest of Samba Dragon Eggs x 10.74%Samba Dragon Kid x 20.74%
Moon Dragon Egg x 10.74%Nest of Moon Dragon Eggs x 10.74%Moon Dragon Kid x 20.74%
Sea Dragon Egg x 10.74%Nest of Sea Dragon Eggs x 10.74%Sea Dragon Kid x 20.74%
Anubis Dragon Egg x 10.74%Nest of Anubis Dragon Eggs x 10.74%Anubis Dragon Kid x 20.74%
Viking Dragon Egg x 10.74%Nest of Viking Dragon Eggs x 10.74%Viking Dragon Kid x 20.74%
Sensei Dragon Egg x 10.74%Nest of Sensei Dragon Eggs x 10.74%Sensei Dragon Kid x 20.74%
Zeus Dragon Egg x 10.74%Nest of Zeus Dragon Eggs x 10.74%Zeus Dragon Kid x 20.74%
    Nest of Crimson Dragon Eggs x 21.14%
In addition to the above, you will receive 1 of the following: In addition to the above, you will receive 1 of the following: Nest of Gargoyle Dragon Eggs x 21.14%
    Nest of Golem Dragon Eggs x 21.14%
Tiny Life Orb x 272.75%Tiny Magic Coin x 272.75%Nest of Grass Dragon Eggs x 21.14%
Life_Orb_2_Root x 125.00%Magic Coin - Bronze x 125.00%Nest of Green Dragon Eggs x 21.14%
Life_Orb_3_Root x 12.25%Magic Coin - Silver x 12.25%Nest of Rock Dragon Eggs x 21.14%
    Nest of Roc Dragon Eggs x 21.14%
    Nest of Sharp Dragon Eggs x 21.14%
    Nest of Spotted Dragon Eggs x 21.14%
    Nest of Toadstool Dragon Eggs x 21.14%
    Nest of Nature Dragon Eggs x 21.14%
      
    
In addition to the above, you will receive 1 of the following:
 
      
    Stone Brick x 272.75%
    Stone Bricks x 125.00%
    Pile of Stone Bricks x 12.25%

You cannot win a dragon, nest or egg reward that is not shown on the wheel at that time. The above probabilities refer to overal probabilities. Each spin of the the wheel will impact the next spin in the following way:
When a segment of the wheel is landed on, all other segments become more likely to be landed on for the next spin. This effect is evenly applied and in the long-run will even out.