Rystil Arden said:
Actually it does not. It specifies that it has the special abilities of a creature of the type and HD. In D&D, Ability scores are not included as a type of special ability. Even though it is not how Simulacrum works by the effect description, I'm curious: in your 10s example, if I copy a level 20 human paladin, does he have all 10s in his stats?
It doesn't actually use the word "type". it just uses "a creature" theoretically, a cruel GM could make your copy of a dragon be, for all purposes, a new kind of creature, "snow golem", that has the listed HD and the feats, skills, special abilities, and such of his snow golem of that HD (including the fact that it starts taking damage (melting) if the temperature rises above freezing

) that just happens to be the shape and color of the dragon you simmed. It's still a duplicate creature (it looks and acts pretty much the same - one reasonable definition of duplicate creature) but it's a totally different type.
Rystil Arden said:
That aside, if all you need is proof that age category is not a function of hit dice, its easy enough. Let's say my dragon takes 5 Hit Dice in Hidecarved Dragon PrC. I don't gain any age categories, so no new DR or SR, but my breath weapon DCs go up (based on HD).
HD and Class levels are treated differently in many, many respects - check out the Increasing hit dice Tables under Improving monsters; specifically, the note about class levels: (srd.pbemnexus.com/improvingMonsters.html)
INCREASING HIT DICE
As its Hit Dice increase, a creature’s attack bonuses and saving throw modifiers might improve. It gains more feats and skills, depending on its type, as shown on Table: Creature Improvement by Type.
Note that if a creature acquires a character class, it improves according to its class, not its type.
Levels in a prestige class are treated seperately.
Rystil Arden said:
Edit: Age category is not a special ability. It is a category. It is like a template being applied on a dragon of the next lower category. It is this category that determines other features. Hit Dice does not determine age category, and Age Category does not determine Hit Dice per se, although each time you apply an extra age category, the dragon does gain 3 HD, in addition to other benefits. So if you simu the dragon, he loses the benefits of his new shiny Hit Dice, but he doesn't lose his very identity, or he wouldn't be a duplicate creature. What about the monsters in the MM3 that exist under separate entries on separate pages but are part of the lifecycle of the same creature (can't remember which ones at the moment). If I simu the big one, does the simu become one of the little guys? No. It stays as a "duplicate creature"
That's one interpertation. Another is that the spell specifies that it has the special abilities of a creature with the reduced HD, and most draconic abilities are special. What's the skills, feats, and special abilities of a black dragon with 12 HD? Asked in that way, a person looks at the summary table, finds a close match on the HD (a 2 HD improved Juvinile), and takes the special abilities off the chart from that row, grabs the age category, and uses that to correspond with the other special abilities appropriet to those HD on the second table.
Now consider consequences of the two methods:
Situation: By definition of the Special Materials, a suit of medium half-plate Black Dragonhide armor (cost: 1,500 gp) required the hide of a dragon of size Gargantuan (medium + 3) which is either a Wyrm or Great Wyrm (when selecting off black Dragons; base CR 20 and 22, respectively). Thus, such a character could, theoretically, use a small piece (after smashing) of such a suit of armor to Sim a dragon. Suppose we have a character who was focusing on power spells, and thus wanted the highest caster level he could get, and he has a character level of 16. So let's see... he takes Wizard up to 13, 3 levels of Archmage (selecting Spell Power each time), and buys an Orange Ioun stone. He has a caster level of 20 (13 wiz, +3 arch, +3 spell power, +1 stone), but spells per day and spells in his spellbook appropriet to Wiz-16. You know, something you might find in a game with characters high enough up to cast Simulacrum.
A sim made from such will thus have 17-19 HD (depending), cost 1700 to 1900 exp, the same in GP for rubies, and a 12-hour casting time (for each dragon). If the character decides to delay leveling up for a while, he can make nine or eight of these with the recources it would take him to reach level 17. Now lets look at party power for the two takes of the spell:
Your take:
Call it 1-2 CR less for the reduction in HD and some abilities, which leaves the sim dragon at CR 18-21; 8 18's (low-end of both variables) would make for a ECL of 24 - "Overpowering" for a 4-character level 17 party. (calculated by
http://www.d20srd.org/encounterCalculator.htm in case you are interested)
My Take:
Those HD translate to an Improved Young Adult or an Adult, CR 9 to 11. 9 of them (high end of both variables) makes for an ECL of 17; "challenging" for a party of 4 level 17 characters.
Which do you think a decent DM would choose?