Dragon Information

Damage determination:

To determine the damage of a breath attack, take the creature's hit points and divide by 3 (except in the case of Lightning, for which you should divide by 4.)

As for resistance, it depends on the type of attack:
Acid
Divide the damage by 2 if you have armor to corrode; divide by 4 if you have resist acid and armor.
Cold or Fire
Divide the damage by 3 if you have permanent or temporary resistance; divide by 9 if you have both.
Lightning
Divide the damage by 3 if you have any kind of resistance.
Gas
There is no resistance! You're hosed!

The Balrog:

Dragon Name
Hit Points
Level		 Attack Type Maximum Damages
No protection Some protection Best protection
Balrog
Hit points: 3000
Level: 100		 Fire 1000 333 111

Ancient Dragons:

Dragon Name
Hit Points
Level		 Attack Type Maximum Damages
No protection Some protection Best protection
Ancient Multi-Hued
Hit points: 2080
Level: 40		 Lightning 520 173 173
Acid 693 347 173
Fire/Cold 693 231 77
Gas 693 693 693
Ancient Red
Hit points: 840
Level: 40		 Fire 280 93 31
Ancient Green
Hit points: 720
Level: 39		 Gas 240 240 240
Ancient Black
Hit points: 720
Level: 39		 Acid 240 120 60
Ancient Blue
Hit points: 696
Level: 39		 Lightning 174 58 58
Ancient White
Hit points: 704
Level: 38		 Cold 235 78 26

Mature Dragons:

Dragon Name
Hit Points
Level		 Attack Type Maximum Damages
No protection Some protection Best protection
Mature Multi-Hued
Hit points: 640
Level: 38		 Lightning 160 53 53
Acid 213 107 53
Fire/Cold 213 71 24
Gas 213 213 213
Mature Red
Hit points: 480
Level: 37		 Fire 160 53 18
Mature Black
Hit points: 464
Level: 37		 Acid 155 77 39
Mature Green
Hit points: 384
Level: 36		 Gas 128 128 128
Mature Blue
Hit points: 384
Level: 36		 Lightning 96 32 32
Mature White
Hit points: 384
Level: 35		 Cold 128 43 14

Young Dragons:

Dragon Name
Hit Points
Level		 Attack Type Maximum Damages
No protection Some protection Best protection
Young Multi-Hued
Hit points: 320
Level: 36		 Lightning 80 27 27
Acid 107 53 27
Fire/Cold 107 36 12
Gas 107 107 107
Young Blue
Hit points: 33d8
Level: 36		 Lightning 66 22 22
Young Red
Hit points: 288
Level: 35		 Fire 96 32 11
Young Black
Hit points: 256
Level: 35		 Acid 85 43 21
Young Green
Hit points: 32d8
Level: 29		 Gas 85 85 85
Young White
Hit points: 32d8
Level: 29		 Cold 85 28 9