Word of the Titans
This is a collection of posts made by Rob Balder on the Giant in the Playground Forums. It is copied here for easier reference and to save the valuable information. It is.. well, the Word of God.
Newer posts first. References to forum posts are mandatory.
How to make a reference to this information in another article: to make a link to post 6012585 - enter [[Word_of_God#6012585]].
You have to understand that the denizens of Erfworld don't see a lot of what a player would see in a game. Including XP. Leveling is a surprise to them, and XP (or the equivalent) is a theory (albeit a pretty solid one). The people are in the dark and guessing, and it's kind of hard to build an XP table by actually finding 10 new level 1 Marbits to croak, discovering that you level, then discovering through experimentation that you need to croak 50 to level again.
From a narrative perspective, the fudge factor is high. But that does not mean there is not one consistent mathematical system governing leveling. It's just opaque to the characters and readers at this time.
The general answer to your question is that power gains are linear and level requirements are exponential. It's not perfectly simple as all that, but to generalize, yes.
The relative combat power by level is NOT logarithmic or exponential.
Higher levels cost more, on a kind of exponential scale that may vary by a large number of factors including the type of unit leveling, the type and number and levels of units croaked, and other activities involving the leveling unit's special abilities that may not even constitute combat. But the main thing is that you should imagine something like a logarithmic curve (not saying it literally is logarithmic), whereby low levels are achievable with a little combat, but levels above 10 or 11 become extremely difficult to obtain, and something like a level 20 unit is completely unheard of. Also notable is that not all of the numbers are available to the units and commanders to calculate, and so the existence of a predicable system of leveling at all is in the realm of the theoretical Mathamancers. Units cannot actually predict when they are going to level (Jillian is being flippant when she tells the Archons, "Cmon, it'll be fun. You'll level." but it would be a reasonable bet they might if they took out a stack of dwagons.)