Converting d20 Challenges

Difficulty Class

Generally the formula is (DC - 15) * 3/5

However, because Hero games typically have a slower skill cap at the top, the following guidelines work well.

DC 5 = +3

DC 10 = +2

DC 13 = +1

DC 15 = +0

DC 16 = -1

DC 18 = -2

DC 20 = -3

DC 23 = -4

DC 25 = -5

DC 28 = -6

DC 30 = -7

DC 33 = -8

DC 35 = -9

DC 38 = -10

DC 40 = -11

I am currently updating my DCV/DEF/OCV guidelines and will post those when ready.

DCV

Base Attack * 3/5 (0.6) + 3

Deflection bonus, Dodge bonus, etc, anything associated with not being hit should be 1/2 and added to DCV (e.g. a +2 Deflection Bonus = +1 DCV)

DEF

Look at Flat-Footed AC. Generally +1 AC = +1 DEF. Natural Armor over +8 should be at 1/2.

Damage Reduction

Apply either as rPD or rED at half value (e.g. DR 10 = 5 DEF) or as Damage Reduction at 25% per 5 DR. Excess is as armor e.g. DR 20/- vs. Fire equals 75% DR and 3 rED)

OCV

Total Attack * 3/5 (0.6) + 3

Improved Attack = +1 with that attack

Weapon Focus = +1 OCV

If a large part of the threat comes from STR adding into melee attack, make 1/2 the D&D STR Bonus into HtH Skill Levels.

Characteristics

(Stat - 10) * 5/4 +10

Generally +4 D&D = +5 Hero

STR

10 = 10

12 = 13

14 = 15

16 = 18

18 = 20

20 = 23

22 = 25

24 = 28

26 = 30

Hit Points

A bit trickier. HP/(8 + CR/2) = # of hits necessary to kill by appropriate level party. 1 CR is about 30 total points.

Hero damage is 2 + total points/15 or 2 + 2*CR (quick calc).

(Take Hero Damage - DEF) * # of hits. This is twice the monster's BODY.

Example: 40 HP, CR 6, FF AC 16 monster = 4 hits to kill. DEF is 6, damage is 14, so 14-6 = 8 * 4 = 32. Since that is the damage to kill, which is 2xBODY, the monster's BODY is 16.

BODY

D&D STR * 0.4 + 6. So a STR 20 monster is 14 BODY.

STUN

I derive from the characteristics, adding 25% DR for each size category.

Spell Damage

Generally 2 DC per Spell Level + 1 DC base with all appropriate advantages. If a spell scales with caster level, use 1/2 the caster's level instead of the spell level. A fireball cast by a 10th level character does 11DC damage.

Environmental Damage

In general, look at the max damage and divide by 3. That is the number of DCs. You decide if it is killing or normal.

Breaking Things & STR Checks

Breaking things is tricky. Hero already has a well defined system for that. However, when it comes to effects like "Characters can escape the sinking sand by making a DC 23 STR check" this table gets it done. Break Effect means total BODY on the STR dice.