My standard joke on roleplaying game editions is that to understand the difference you need to know how many arrows it takes to kill a level 1 mage. Of course that is a caricature, but like all caricatures there is a core of truth in it: A game in which your level 1 character can be killed by one single arrow feels inherently very different than a game where it takes half a dozen arrows to kill a level 1 character. And especially 4th edition and 5th edition Dungeons & Dragons are on opposite extremes of that scale: 5E is fast and deadly, 4E is more predictable and tactical.

The different "feel" of combat is based on simple mathematics. Imagine you have a character that deals 2d6 of damage, so his average damage is 7 points. If he has a 50% chance to hit something, then on average he deals 3.5 points per round of combat. Compare that to the hit points of his opponent, and you will find that it takes that character on average 3 turns to kill an opponent with 10 hit points, and 6 rounds to kill an opponent with 20 hit points. You can do the same calculation in the other direction, and that gives you a prediction of who will win the fight. If on average it takes the player 3 rounds to kill the monster, while on average the monster will take 5 rounds to kill the player, the player is likely to win that fight.

The peculiarity of 5th edition is two-fold: First damage numbers are high in 5E (e.g. a magic missile does more damage in 5E than in any other edition of D&D) and the hit points are more on the low side, half of what they are in 4E. So already here it becomes clear why combat in 5E is much faster. But second there is an additional factor, which is how likely the results are to deviate from the average. 5E has the most extreme deviations from the average, the above described character with his 50% chance of dealing 2d6 damage and an average damage per round on 3.5 can with a critical hit and maximum damage roll deal 24 points of damage, killing his 20 hit points opponent with a single stroke instead of needing 6 rounds. So combat in 5E is a lot less predictable than in 4E or Pathfinder, and to me sometimes even feels a bit random: Extreme dice rolls play a bigger role in determining the outcome than any tactical maneuvers. The slower pace of 4E is deliberate, as having more rounds of combat makes tactical choices more important, like the resource management part of the use of daily and encounter powers.

So if I wanted to convert the Zeitgeist adventure into 5th edition, the different feel and lack of predictability would cause me a problem. The campaign is rich in story, and there are some fights which for story reasons should be predictable, for example the very first fight in the campaign where the players as police are arresting some troublemakers, a fight which they are supposed to win without problems. Having an accidental player character death in that fight would be quite detrimental to the rest of the story. I could imagine other styles of campaign of a more sandboxy sort where the randomness of combat provides impulses to the improvised interactive story-telling. But for the campaign style of Zeitgeist 5E is a lot less suited. So I gave up on the idea.

In other news, we just did an "intermission" session to level up the characters of our Zeitgeist campaign to level 2, including kitting them out with more magic items from the RHC stores (another point where the Zeitgeist campaign differs from typical D&D campaigns in which you "find" magic items). Then I explained to the players the different quarters of the city of Flint, where the next adventure plays, and allowed them to freely invent two contacts from two different quarters. That is to encourage role-playing and fostering creative ideas for alternative routes in the next adventure by "using people you know" (for reference, the concept of "you are who you know" is very prominent in the Shadowrun pen & paper roleplaying game, but hey, one can always borrow good ideas from other systems).