I'm not talking about scaling 'encounters' to the PCs' capabilities in anything other than a rough and ready fashion. I'm certainly not talking about some analog to CRs or other balancing mechanic designed to maintain an even level of pressure on the characters. I think that's a false idol, both unattainable and undesirable besides.
No, I mean something much simpler: D&D and GURPS consider different things to be difficult, and they favor different sorts of tactics.
D&D at its core involves tactics of resource management and attrition. Roughly speaking, the slope of the increase in hit points for a party is about twice that of the slope of damage output increase for a party. (I'm eyeballing it here; the main point is that it's proportional with some multiplier n.) In GURPS, if anything, it's the opposite; what with points for Targeted Attacks and Weapon Mastery and Heroic Archery and more damaging spells and whatnot, damage increases as about twice HP.
This is reflected in the different challenges in the two games. In D&D, in order to have a monster fight that challenges higher-level characters, you throw bigger monsters with stronger attacks at them - you're still presenting a serious threat to their resources without necessarily killing them outright, and you're pretty well guaranteed to have your monsters stick around long enough to be interesting, since they're bringing enough HP to the fight that the PCs can't get rid of it fast enough to be trivial. Conversely, in GURPS if you try this tactic, you're going to end up with a very quick fight - either the PCs will walk all over your big nasty, or you'll accidentally squish the party.
Instead, in GURPS, the general tactical layout involves multiples of smaller monsters, because smaller monsters can still pose a serious threat, and dividing up the foes divides player actions. In other words, D&D is about managing hit points, whereas GURPS is about managing actions. The side with more actions is the side with the advantage.
This is borne out by the common advice for encounter balancing in GURPS. It's often said that, if pitting the PCs against a singular large monster, you should do one or more of:
- Give the monster Extra Attacks, always-on effects, or suchlike, thus bringing number of available actions back toward parity
- Give the monster special defenses, such as insubstantiality or injury tolerance, thus making each opposing action less effective
- Include environmental effects, thereby requiring that PCs spend their actions on things other than killing the monster
- Provide tactical advantage to the monster, which reduces PC actions either entirely (e.g. surprise) or in their effectiveness (e.g. an archery battle against an enemy up-hill - which means that PCs either shoot back at minuses or spend actions closing the distance).
This is something of a problem for the Temple of Elemental Evil, which naturally assumes a D&D approach to combat tactics. For example, there are places in the modules where a single ogre (or an ogre and a wolf, later on) is put forward not only as a foe, but as very stiff opposition that the party will probably flee from. In GURPS, on the other hand, a party of 50-75pt characters can probably take out a single ogre without much difficulty - maybe one death, if the ogre gets in a lucky hit. So how to convert these?
It turns out the answer is, "only partially", at least for my purposes.
The pivot point between GURPS and D&D works both ways. There are encounters that are supposed to be very tough in D&D that the GURPS characters will walk right over. However, there are also encounters that Gygax reckons will be fairly easy for a group of 4th-5th level D&D characters that will present serious problems for GURPS characters even at 300 pts. (I'm looking at you, group of 25 bandits.) There are enough of these that I think it balances neatly enough, even if sometimes it looks like they're in the wrong places.
The other part is taking a hard look at the large monsters that the Temple favors for challenging PCs and seeing if there isn't some way to preserve some of that element. To that end, let's take ogres are our example du jour:
Ogres in D&D are fairly nasty, especially toward lower-level characters. To help preserve that, in my game, all ogres will have Magic Resistance 5. This, combined with the extra casting cost to directly affect creatures of larger sizes, should put a damper on magical solutions that don't mimic weapons or environmental effects. Further, while they're stupid, they will have a canniness that enables them to use their advantages well. They will all get Tactics-12. Specifically, while they can't really hide (even if they could find a place not to be seen, you'd still be able to smell them), they naturally pick lairs that enable them to use their reach and their greater strength to advantage, doing things like picking places with attached hallways or stairs, and piling up obstacles that create difficult footing for creatures not as large. Finally, ogres in my game have extra DR 3 over vitals and the skull, in the form of thick subdermal ridges of bone, making them look burly even for their size and giving them low, sloping foreheads with weird, angular planing. Evolution has taken advantage of this, layering on extra muscle at these reinforced attachment points, which explains their high strength.
So, in my game, an ogre looks something like this:
|ST: 25||HP: 25||Speed: 6.00|
|DX: 11||Will: 7||Move: 6|
|IQ: 7||Per: 7|
|HT: 13||FP: 13||SM: +1|
|Dodge: 9||Parry: 10||DR: 2, 5 on vitals and 7 skull|
Punch (13): 2d+2 cr
Club (14): 5d+3 cr (treat as oversized maul, meaning it's 0U because of strength)
Traits: High Pain Threshold, Magic Resistance 5, Night Vision 7 DR 2 (Tough Skin), DR 3 (Limited: Skull, Vitals), Bad Temper, Bully
Skills: Brawling-13, Tactics-12, Two-Handed Axe-Mace-14
Notes: Some may have armor, mostly on the chest; adjust DR accordingly. (Most common is either naked or Heavy Leather.) Willing to negotiate, but only on their level (Food, women, territory, simplistic praise), easily tricked.