Before you translate an AD&D monster to RuneQuest, make sure that you need to. RuneQuest already has a lot of creatures.
Unlike AD&D, RuneQuest monsters aren't all cookie-cutter identical. They have characteristics and skills just like characters. Evidently, AD&D was written before the concept of "design elegance" had penetrated the gaming world. Nevertheless, translations can be done.
This method will give you the average values for these critters. Divide this average by 3.5 to determine the number of 6-sided dice to roll when generating a creature. Any remainder can simply be used as a bonus. Thus, an animal with an average STR of 12.5 would be rolled as 3D6+2 (12.5/3.5=3 with a remainder of 2). In all cases, if the AD&D description of a creature actually lists an characteristic, convert the characteristic as above instead of using the following.
Calculate all Attributes as in RuneQuest from the RuneQuest Characteristics. To calculate RuneQuest Move, divide the AD&D Movement by 3, round to nearest whole number.
The creature's Armor Points can be found by subtracting the AD&D armor class from 10.
Damage is either by RuneQuest weapon, modified by RuneQuest Damage Bonus, or if it is a natural attack, a claw does 1D6. A hoof does 1D4. A bite from a carnivore/hunting animal does 1D8. Bites from all other creatures do 1D4. Remember to add the RuneQuest Damage Bonus to this base.
Damage from innate magical abilities that do hit point damage is equal to the creature's RuneQuest CON or the original AD&D damage, whichever is lower.
Skill with attacks is converted as THAC0 is converted for characters.
A lot of AD&D creatures have weird abilities. Translate these as magical effects. Where a "saving throw" is specified, match the creature's MP vs. the target's MP on the RuneQuest resistance table. Each use of such a power may or may not use MP, depending on how the power works. A good rule of thumb to use is that whatever could kill a man outright should cost five or six MP, and scale accordingly. "Level Drain" would translate as 1d3 to 1d6 drain of Fatigue or MP.
Assign other skills by what makes sense to you.
The Ogre is the mainstay of low to mid-level AD&D adventuring. The RuneQuest conversion would go thus:
The Ogre is listed as having a Str of 18/00. This is converted as 20.
An Ogre has 4 Hit Dice, giving it an average CON of 14.
The AD&D Size of an Ogre is "L", but it's still only around 9 feet tall, so we'll give it an average SIZ of 20, the low end of the SIZ conversion for "L".
Ogre INT is 9 (AD&D 8 plus 1).
POW is 11 (half of hit dice plus 9).
Ogre DEX is 10.5 (no evidence one way or the other).
Ogre APP is 6.5 (ugly, vicious brutes, 10.5 minus 2 then minus 2.)
Innate armor points are 5 (10-AC of 5), but they could wear other armor if anybody would give it to them and they fit.
Base damage is by weapon or 1D3 (fist) plus Damage Bonus.
An Ogre's base ability with an attack or a parry is 39%.
Ogres have no weird abilities.
So, dividing characteristics by 3.5 to give dice and calculating attributes, we have the following:
AD&D Ogre Converted for RuneQuest
Dice Avg.
STR 5D6+3 20-21 Move: 3
CON 4D6 14 Avg. Hit Points: 17
SIZ 5D6+3 20-21 Avg. Fatigue: 34
INT 2D6+2 9 Avg. Magic Points: 10
POW 3D6 10-11 DEX SR (avg.) 3
DEX 3D6 10-11
APP 2D6 7
Armor: 5-point skin, all locations.
Weapon SR Attack Damage Parry Points
Fist 6 39%+5% 1D3+2D6 39%-5% --
Maul 4 39%+5% 2D8+2D6 39%-5% 16
Skills: Sneak 40%, Hide 50%, Track 30%
Magic: Whatever is appropriate for a warrior in this campaign.
Djinni are far more difficult to convert, since they have so many special abilities. I won't run through converting the non-weird stuff and cut to the chase.
The various creation abilities of Djinni can be converted as summoning abilities. The Djinn summons these items from either another plane of existence or fairly nearby, depending on whether you're a nice GM or a sadistic GM. The illusions of a Djinn function either as the Divine Illusion spells or the Sorcerous Phantom (sense) spells, depending on whether you consider the power of Djinns to be truly other-worldly or merely "mundane" magic.
The invisibility, gaseous form, windwalk, and whirlwind abilities should be replaced simply with the ability to assume the form of a RuneQuest Sylph (air elemental), basically the equivalent of those physical abilities.
The wish-granting abilities of Noble Djinni can be simulated as the ability to cast any Spirit, Divine or Sorcery spell (up to a maximum intensity of 10 for sorcery or spirit magic and up to a maximum of 5 points of Divine magic at a time.)
The final result is below:
Djinn
Dice Avg.
STR 6D6+1 22 Move: 3, 8 flying
CON 4D6+3 17 Avg. Hit Points: 19
SIZ 6D6+1 22 Avg. Fatigue: 39
INT 3D6 10-11 Avg. Magic Points: 11
POW 3D6+1 11-12 DEX SR (avg.) 3
DEX 3D6 10-11
APP 3D6 10-11
Armor: 6-point skin, all locations.
Weapon SR Attack Damage Parry Points
Fist 6 51%+7% 1D3+2D6 51%-6% --
Skills: Your guess is a good as mine, probably lots of social skills and
lore.
Magic: Summon food, summon water/wine, summon soft goods, summon metal,
Illusion Sight and Illusion Sound or Phantom Sight and Phantom Hearing, able
to transform into a Sylph of the same SIZ at will.