OSRIC to Mothership Conversion

 This is pretty much my OSE to Mothership rules with included tweaks form my previous analysis and the slight adjustments required to go from OSE to OSRIC extra features.

HD +1 = Wounds

HP = Health, if HP is under 10, add +1d5+6 (Allowing 1 or less HD monsters to have between 11-15 Health), add the HD modifier to Health if average not listed.

At the Warden's discretion, really small animals can just keep the HP as Health for being fragile.

If 4 Wounds or higher, deduct 2 Wound and 10 Health for every 3 total Wounds.

If this reduces the new Health total to 10 or less, add 10 to the Health. and round up to the nearest 10.

If the Warden does not like the high Wound and low Health end result, they can halve the Wounds and double the Health.

Combat = 21 -THACO + Any listed modifiers x5 +15, or Ascending Attack Bonus +2 + Any listed modifiers x 5 +15.

Instinct = HD x 10, becoming HD x 5 after 5 HD, as a percentage

Every 4 or fraction thereof of the OSRIC bonus HP becomes an addition +5% to Instinct

(9-AC/AC-10 for Ascending) round down = AP

For NPCs AC becomes (10-AC)/2 with rounding down = AP. This accounts for the original rules OSRIC is derived from miscalculating based on an older edition, prior to printing. If not corrected in future editions to (requiring 9-AC), it remains as such.

d4 = d5

d6 = d10

d8, d10, 2d6 = 2d10

Doubling as you go

Once you get to 4d10, you have the option of changing it to 1 Wound if caused by massive damage.

Bonuses to damage are ignored unless they are +2, then up the dice by one per +2 on the chart prior to converting.

If a + Weapons is required to hit the monster, deduct 1d10 from the damage of the Mothership weapon per + required.

Anytime something that Mothership handles with a percentile roll is rolled on a D6, multiple the chance of that by 16.666 and round up.

Probably should do a demonstration:
OSRIC, one random page gives me Treants.

Treant

frequency: Rare

no. encountered: 1d20

Size: Large

move: 120 ft

armour class: 0

hit dice: 7-12 (1d6+6 if randomly determined)

attacks: 2 (fists)

damage: See below (depends on HD)

Special attacks: Animate trees

Special defences: Cannot be surprised

magic Resistance: Standard

lair probability: 10%

Intelligence: Very

alignment: Chaotic good

level/xp: 7HD: 1,295+8/hp 8HD: 1,600+10/hp 9HD: 2,050+12/hp 10HD: 2,350+13/hp 11HD: 2,750+14/hp 12HD: 3,600+16/hp

Treants are woodland creatures, reclusive to humankind but friendly with other good aligned creatures of the woods. They resemble humanoid trees: their “arms” and “legs” are not easily seen as such until they begin moving. Treants are vigilant guardians of the woods, despising anyone of evil alignment and all who make reckless use of fire, regardless of alignment. Treants can animate 1d2 trees to aid them (see “Tree, Animated”) within a range of 180 ft. Separate experience is not awarded for killing such animated trees. Treants are quite vulnerable to fire: fire attacks requiring a roll to hit gain a bonus of +4, a treant makes saving throws vs fire at –4, and any hit die of damage inflicted upon a treant gains a +1 to its result. Damage inflicted by a treant’s clubbing fists is determined as follows: 7-8 HD: 2d8 damage per fist 9-10 HD: 3d6 damage per fist 11-12 HD: 4d6 damage per fist

Treasure: 10d4 gems (50%); 2d4 potions (40%)

Wounds: d6+6, +1 = lets start with an average 11 Wounds

Health per Wound: 4.5 x 11 = 50

If 4 Wounds or higher, deduct 2 Wound and 10 Health for every 3 total Wounds.

3 time deduct 2 and 10 health = 5 and 20 respectively

Combat = 21 -THACO + Any listed modifiers x5 +15, or Ascending Attack Bonus +2 + Any listed modifiers x 5 +15.

A 10.5 HD monster has a THACO of 11, so 21-11 = 10 x 5 + 15 = 65%

Lists 2 attacks a round

Instinct = HD x 10, becoming HD x 5 after 5 HD, as a percentage

10.5 - 5 = 5.5, so 50%+27.5% = 78%, lets just round it to 80%

Every 4 or fraction thereof of the OSRIC bonus HP becomes an addition +5% to Instinct

Movement 120', so as fast as a human

Treants may have high HD but no +s ontop of that

(9-AC/AC-10 for Ascending) round down = AP

9-0 = 9

Damage 4d6 per fist = 4d10 or 1 Wound

d6 = d10

Once you get to 4d10, you have the option of changing it to 1 Wound if caused by massive damage.

No bonuses to damage

No special defences to elements

Anytime something that Mothership handles with a percentile roll is rolled on a D6, multiple the chance of that by 16.666 and round up.

Cannot be Suprised in the forests, can summon 1 or 2 Animated Trees (lesser relatives?)

+4 to hit with fire and -4 to save against fire on a D20 sounds like [+] and [-].
Extra damage is fairly easy.

Intelligence is already represented by their high instinct and Magic resistance is standard, so not worth discussing.

Woody Aliens of Fangorn 2

W5(20)

COM 65% Attacks 2 (4d10)

AP 9

As fast an unencumbered human

Always knows where the party is when they are within it's range

When in it's forest home, can summon lesser relatives

Attacks using Fire break AP

Takes [+] Damage and Wound Rolls from Fire