Converting original D&D and Mystara monsters

Lets make a start.

Mek
Large Construct
Hit Dice: 11d10+30 (90 hp)
Initiative: +1
Speed: XX ft. (X squares)
Armor Class: 24 (-1 size, +1 Dex, +14 natural), touch 10, flat-footed 23
Base Attack/Grapple: +8/+22
Attack: Slam +17 melee (5d6+10)
Full Attack: 2 slams +17 melee (5d6+10)
Space/Reach: 10 ft./10 ft.
Special Attacks: Breath weapon
Special Qualities: Construct traits, damage reduction 10/adamantine, darkvision 60 ft., immunity to magic, low-light vision
Saves: Fort +3, Ref +3, Will +3
Abilities: Str 30, Dex 12, Con --, Int --, Wis 11, Cha 1
Skills: --
Feats: --
Environment: Any
Organization: Solitary
Challenge Rating: XX
Treasure: None
Alignment: Always neutral
Advancement: 12-14 HD (Large), 15-16 HD (Huge)
Level Adjustment: --

Breath Weapon (Su): 10-foot cube, cloud of paralyzing gas lasting 2d4 rounds, free action once every 1d4+1 rounds; Creatures within a cone of paralyzing gas must succeed on a Fortitude save (DC 15) or be paralyzed for 1d6 rounds. The save DC is Constitution-based.

Immunity to Magic (Ex): A mek is immune to any spell or spell-like ability that allows spell resistance. In addition, certain spells and effects function differently against the creature, as noted below.
A magical attack that deals cold damage slows a mek (as the slow spell) for 3 rounds, with no saving throw.
A magical attack that deals fire damage breaks any slow effect on the mek and heals 1 point of damage for each 3 points of damage the attack would otherwise deal. If the amount of healing would cause the mek to exceed its full normal hit points, it gains any excess as temporary hit points. For example, a mek hit by a fireball gains back 6 hit points if the damage total is 18 points. A mek gets no saving throw against fire effects.

A mek is affected normally by rust attacks, such as that of a rust monster or a rusting grasp spell.

Does that look ok so far?

Regards
Mortis

Lookin' good.

Speed translates to 30 ft.

Meks attack by striking with their heavy metallic limbs, inflicting 5d6+10 points of damage with each of their two mighty fists. So great is a blow from one of these monstrosities that a creature hit by both fists in one round must make a saving throw vs. paralysis. A failed saving throw means that the mek has knocked the victim off his feet, stunned for 1d4-1 rounds. If the saving throw succeeds, the victim still falls prone.

Click to expand...

Heavy Blows (Ex): A creature struck by a mek's slam attack must succeed on a DC X Fortitude save (?) or be stunned for 1d4-1 rounds and fall prone in its space. Even with a successful save, the victim must succeed on a DC X Balance check or fall prone in its space. The save and check DCs are Strength-based.

Shade said:

Heavy Blows (Ex): A creature struck by a mek's slam attack must succeed on a DC X Fortitude save (?) or be stunned for 1d4-1 rounds and fall prone in its space. Even with a successful save, the victim must succeed on a DC X Balance check or fall prone in its space. The save and check DCs are Strength-based.

Click to expand...

Meks attack by striking with their heavy metallic limbs, inflicting 5d6+10 points of damage with each of their two mighty fists. So great is a blow from one of these monstrosities that a creature hit by both fists in one round must make a saving throw vs. paralysis. A failed saving throw means that the mek has knocked the victim off his feet, stunned for 1d4-1 rounds. If the saving throw succeeds, the victim still falls prone.

Click to expand...

Should we alter Heavy Blows to reflect that both slams have to hit (a little like a rake), if so we would have

Heavy Blows (Ex): If a creature is struck by both of the mek's slam attacks in the same round it must succeed on a DC X Fortitude save (?) or be stunned for 1d4-1 rounds and fall prone in its space. Even with a successful save, the victim must succeed on a DC X Balance check or fall prone in its space. The save and check DCs are Strength-based.

Regards
Mortis

Good catch. The revision looks good.

Added to Homebrews.

Looks good.

DCs for Heavy Blows are 25.

As its about two-thirds of an iron golem does CR 8 seem reasonable. Perhaps CR 9 would be better due to the Heavy Blows DCs?

Even though the text metioned that the secret of making a mek has been lost, we should still include a construction section.

Does 3,000 lbs seem reasonable for its weight?

Then its 'just' flavour text to go.

Regards
Mortis

I'd say CR 10. The clay golem also has 11 HD and is CR 10, and the mek has a higher damage output. The clay's better DR, haste, and cursed wound probably help balance it out with the heavy blows and paralysis gas.

All the rest looks good.

Perhaps CR 10 would be fairer

Regards
Mortis

Updated Homebrews.

Just construction to do, and then its on the the elementals of law and chaos.

Regards
Mortis