I often need to convert monsters between editions. I still have a preference for 1e modules over almost anything published later by TSR or WotC. I run my campaigns in Eberron, and a lot of really good material for that setting was published in 3.5e. And I am beginning to think about playing 5e for casual games (because, while I love 4e, it is a real pig to use without computer assistance, and I can’t expect casual gamers to load the necessary software for a pickup game).
The problem is, monsters in 1e or 3.5e are not necessarily at the same power level in relation to the characters as are monsters in 4e. For example, a first level party of five PCs fighting 5 bog-standard hobgoblins is going to have a pretty hard time of it in 1e, but a relatively easy time in 4e.
The usual advice is to just take the standard monster and add or subtract them until you have an appropriate challenge. But there are several problems with this. First of all, you have to determine what is an appropriate challenge, which is particularly difficult in converting from 1e because CR and EL mechanics did not exist. Then, once you have done that, it requires an additional calculation to figure out the appropriate number of creatures. This may or may not work in the space; 1e dungeons often feature small rooms and can’t afford the space the extra creatures take up. It can also change the feel for the battle, and often the number of creatures is tied to the potential out-of-combat. And sometimes the difference in power level is so great that the encounter can’t be recreated without a serious rebuild.
Since a lot of monsters get used over and over, it is better to build an equivalent monster once, and simply use the same number of monsters as appear in the original module. So for example, I build the equivalent of a 1e hobgoblin one time, and if the module calls for three of them I just use three of them.
In order to do that, I need to estimate the monster’s strength relative to a party of characters in the edition I am converting from; and then build a monster of equivalent strength in relation to the party of characters in 4e. And the first step in that process is comparing a 4e character to a 1e or 3.5e character.
To determine the baseline for comparing characters across edition, I look at what game-affecting resources the characters have access to. And that usually comes down to magic.
There is a quote from James Wyatt, which I copied once but haven’t been able to locate on the web since, which shows how the game evolves with access to certain types of magic. He said:
The Big Milestones
There’s not a huge difference between 1st- and 2nd-level spells in terms of their effect on the world, but once spellcasters gain access to 3rd-level spells, things start to change. Suddenly, characters can fly, damage large numbers of foes with spells like fireball and lightning bolt, and even breathe underwater. Spells of levels 3 to 5 include some of the most iconic spells in the game, such as dimension door, confusion, phantasmal killer, cloudkill, cone of cold, and teleport, to choose just from the wizard’s spell list. Acquiring those 5th-level spells—teleport, scrying, flame strike, and raise dead—is a pretty big milestone, too.
With 6th-level spells, we get into the territory of spells that really change the way adventurers interact with the world. It’s not so much the big, flashy spells—disintegrate, blade barrier, and heal, for example—but behind-the-scenes spells like word of recall, find the path, contingency, true seeing, and legend lore that start changing the way you play the game. Each spell level after that point introduces new effects with a similarly large impact.
When characters get 9th-level spells, they’ve just about reached the pinnacle of their class abilities, and their spells can reshape reality.
As near as I can tell, in all of the editions that primarily use Vancian magic (that is, all editions other than 4e), the game-changing spells usually appear around the same level. For example, I know that in 1e, 2e, 3e, and 5e (and I think in OD&D and BECMI but I don’t have the books to check), Fly was a third level spell which casters received around 5th level.
So for all of the editions other than 4e one can assume that the levels are more or less equivalent. But with 4e it is a bit harder, because the designers intended those milestones to occur at different levels. For example in 4e, encounter-long tactical flight does not arrive until at least 9th level, depending on the class.
To quote from that same article:
While we were designing 4th Edition, we tried to group these big game-changing effects into three tiers of play. We figured that the heroic tier (levels 1–10) was about equivalent to 3rd Edition’s levels 1–5, with magic fairly limited so mundane equipment and skills were more important. Paragon tier (levels 11–20) would introduce tactical flight and teleportation, fast travel, invisibility, mind reading, and similar effects that 3rd Edition gave out over levels 6–14. Then epic tier (levels 21–30) gave characters access to flight and teleportation as travel, resurrection, group invisibility, and pervasive magical effects.
I pretty much follow that, simplified somewhat so I can make calculations in my head. So 4e levels 1-10 are about equivalent to levels 1-5 in any other edition; 4e levels 11-20 are the equivalent of 6-15 (better to map 10 levels to 10 levels than to map 10 levels to 9 levels in my head); and 4e levels 21+ are equivalent to levels 16+. So when converting a character to 4e, if the level is less than five I double it, and if it is more than five I don’t double it but I add five to it. That means a first level character in 1e or 3.5e is equivalent to a second level character in 4e.