Survival Mode

Survival Mode was added in version 1.6. It can be found at the bottom of the world map, northeast of the rock golem. The game describes Survival Mode as:

  "Kill as many monsters as you can before you drop! The reward gets better as you kill more monsters, and you can see how you rank on the Gamecenter leaderboard." 

You do not gain experience or gold during Survival Mode battles, but do get high level gear that can't be obtained anywhere else in the game. The quality of the gear depends on what wave you make it to: Item that is dropped is not tied to what wave group, but the actual wave itself. Say if you got a Dragonscale Shield at wave 8, and kept getting it every time you died on 8, that does not mean you would get the same if you died on wave 7, but it would be around the same value (in this case relatively cheap). You could get a Shooter cloak +1 instead.
 * 1-8
 * 9-18
 * 19-30
 * 31-45
 * 45+

If you retreat from a Survival Mode battle you will still receive a reward for the wave level you were at when you retreated.

Possible Rewards (in progress; feel free to add missing items)
You can get one of the following rewards (and possibly something else), when you retreat in the following waves:

1 - Nothing (You have to finish Wave 1 before you can get a reward)

2-5 - Subtle Knife, Medium Shield, Waraxe, Leather Armor, Leather Helmet

6-8 - Shooter Cloak, Magic Bow, Staff (Superior)

8-10 - Dragonscale Shield

11-12 - Unknown

13 - Warhammer

14-29 - Unknown

30 - Magma Staff

31-32 - Unknown

33-36 - B loodlust Blade, Emblazoned Blade, Red Dragon Helmet, Shielding Brooch

37-40 - Unknown

41 - B lack Archmages Robe

42-45 - Unknown

46+ - G olden Crescent, Spirit Bow, Raconteurs Staff, Deviltongue, Hammer of Thor, Stalkers Ring

Bosses
5: 2 Golems

9: Iron Golem (Name not Official)

13: Heroes (Cleric, Fire Mage, Archer, Fighter) (?)

17: Knight (Name not Official) (?)

21:

25: 3 Heroes (Cleric, Archer, Fighter)

29: Earth Golem and Floating Skeleton (Names not Official) (?)

33: 4 Heroes (Cleric, Fire Mage, Archer, Barbarian)

37:

41: 5 Heroes (?)

45: Lich

49: 4 Iron Golems (?)

53: