In the Ampersand article in this month's DDI, there is a preview of the DMG II - its a description of monster themes made explicit with great examples using Demagorgon's henchmen. Basically, one can add a power to any given creature that may be a worshiper or server of Demagorgon that gives them a little more of Demagorgon's flavor. Themes can be anything, although most of the example are creatures that belong to a certain sect or worship a particular deity.
I love this idea. In fact, I plan to start using the idea right away by giving some Orcus theme powers to undead and demonic creatures in the Demon Queen's Enclave adventure. Using monster themes is a simple idea, but has great potential.
I definitely applaud more ability to customize monsters - I'm just hoping there are a bit more focused guidelines than what they have here, or at the very least, some decent advice for DMs who want to use these and how to account for the monster's increased power.
My sense is that any advise won't be more specific than those given in the DMG for monster creation. Monster creation, customization, etc, seems to be more of an art than a science in 4e. My recommendation is to determine what the powers may mean for your encounter. If you only give one power to one creature in the encounter, then it probably won't have much of an effect as far as the encounter's difficulty. However, if you create an encounter of acid spitting kobolds, then perhaps you'll want to level the creatures up or replace one of their powers.
Just some thoughts. I see the monster levels and encounter levels as more of a guideline than a strict dictate. I've definitely experienced some encounters more challenging than others of the same level depending on terrain, traps, monster combinations, and other factors.
Yeah, I could see how a DM could abuse the idea if not give guidelines or limitations. However, for my game (and certain a lot of others), this concept will add a certain level of depth. We'll just have to wait (October is it?) to see if they provide any further suggestions for adding such powers.
I'm back and forth on this issue. I mean I abused the CR system in 3.5 as a DM. It was so codified that it almost invited me to crack it. If things are just left up to the DMs discretion then unbalanced encounters that don't pay the required XP are he DMs fault.
That said it'd be nice to have something akin to guidelines. I mean its not exactly a step in the right direction if, instead of deliberately ripping my players off, I'm doing so by accident because there are no instructions that help a DM judge when something is bumped up.
Perhaps the best bet is to only add or replace powers of similar type & potency as what is already common for that type of creature. Theoretically, until/unless you start adding more attacks per turn, a monster can have any number of options available without changing its numerical effect on the game.
The number of monster powers is just a question of how much variety you need for the number of rounds you might expect it to last. A Lvl 1 creature is a one-trick (or two-trick) pony b/c it's only going to take one or two successful hits to take it out. Maybe Lvl 3 demon cultists only last 4-6 rounds, so they only need 3-4 different combat powers (and maybe a thematic bonus of some kind when fighting alongside other worshipers).