Now lets get this straight from the outset, though these genetic mistakes of nature have walked the land since the beginning of ages, they are in no way shape or form a race unto themselves.
Therianthropes are those unfortunates who have contracted the disease Therianthropy through one of four ways:

1. They fell into a cursed spring of water and now whenever they encounter mundane water the same temperature of that cursed spring water they change into an alternate form that suits their personality.

2. They unthinkingly insulted some great and powerful Mage/Deity/Spirit, and in terrible retribution said being took it upon itself to turn them into a (Humiliating new form here)  whenever you undergo
(Transformation circumstances here).

3. The person was valiantly fighting, or fleeing, a Therianthrope who took it into its head to bite said person and therefore said person contracted Therianthropy and now turns into whatever the Therianthrope who bit him/her is under whatever circumstances the biter suffers.

4. Finally, and most unlikely of all, some thin line of the disease runs through the family of the person and he/she somehow had the bad luck of contracting it.

    Therianthropes are people of any race who have contracted in some way or another a disease that turns them into anything from the opposite sex to a Dragon.
Elf, Dwarf, Human, Shurani ect. . .it doesn't matter, Therianthropy is a condition that is incurable.
If you want you can decide to start out as one, sometimes the ability to change into something else can be useful, and it can make for a truly interesting character.

    No one gets to choose what they want to be, here is a list of creatures each assigned a number, the player rolls a D100 or percentage dice (2d10s.)  Whatever number he receives is whatever he is doom--err blessed to change into under whatever conditions the game master decides.

Example conditions for transformation:
1. Getting hit with hot/cold water triggers the transformation, getting doused with the opposite temperature reverses the transformation.

2. Emotions can be your trigger, like anger, fear, or sadness, even love.  Whenever the character feels these emotions it triggers the change, feeling this emotion again reverses it.

3. Excitement can be your bane, sexual arousement can trigger your change, or just plane old adrenaline.

Just remember these are examples, an imaginative, and sadistic GM can come up with just about anything that triggers a change, for I care it could be the sight of yourself in the mirror, or the light of the moon, maybe even an allergy of some sort, whatever you come up with be creative and have fun with it.

Form List
1. Newt
2. Roach
3. Fly
4. Mosquito
5. Rat
6. Rabbit
7. Cat
8. Pig
9. Piglet
10. Dog
11. Elf
12. Human
13. Dwarf
15. Drow
16. Woodsprite
17. Sherani
18. Ogre
19. Vampire
20. Wolf
21. Gecko
22. Bear
23. Eagle
24. Pidgin
25. Vulture
26. Zombie
27. Wren
28. Sparrow
29. Robin
30. Ghoul
31. Skeleton
32. Dire Wulf
33. Dread Wolf
34. Orc
35. Goblin
36. Hob Goblin
37. Imp
38. Spider
39. Fairy
40. Dryad
41. Merman
42. Fullen
43. Caterpillar
44. Lynx
45. Tiger
46. Panther
47. Lion
48. Mouse
49. Crow
50. Opposite Sex
51. Albino
52. Abomination  (When you change into this creature your appearance level drops to -4.)
53. Flea
54. Tick
55. Bat
56. Mite
57. Leech
58. Horse
59. Giant Spider
60. Sand Spider
61. Goldfish
62. Dolphin
63. Shark
64. Octopus
65. Ant
66. Squid
67. Crab
68. Lobster
69. Sand Crab
70. Hawk
71. Falcon
72. Human
73. Scorpion
74. Hill Giant
75. Frost Giant
76. Fire Giant
77. Firbolg
78. Ghost
79. Green Slime
80. Yellow Slime
81. Orange Slime
82. Frog
83. Toad
84. Iguana
85. Slug
86. Snail
87. Dear
88. Stag
89. Owl
90. Unicorn
91. Cow
92. Sheep
93. Ram
94. Bull
95. Lichen
96. Mold
97. Fungus
98. Rock
99.  Tree
100. Dragon (Type of Dragon is also rolled for.)