This is a great game. I played it years ago and come back for another round every few years when I'm feeling nostalgic.
In general the game is relatively easy with all clans, so what I like to do is figure out for each clan what the lowest level is that can achieve all of the following in the same run:
* Great Mage (including having defended the title from the challengers)
* #1 ranked
* beat the secret boss
(no attempt is made to win the first encounter with the assassin, except with Poison Water who can do it without sacrificing the rest of the run. Dark Wood is confirmed possible but would use a clan skill that's never used ever again in the entire run so it would push the minimum level up to 80 which is unacceptable. Haven't found a way with other clans yet, if that's even possible.)
As we all know, the lowest possible level that can become ranked #1 is 64, because otherwise arena enemies do not show up at rank 27 (64 * 1.25 = 80, and only level 80 or above enemies show up at ranks 27 and 19).
Also as we all know, the enemy behaviour is deterministic, except for the following four cases:
* 50% chance to use Freeze Defense
* 50% chance to use Silence
* If player knows Poison Wave, 50% chance for the enemy to use Poison Wave (obviously only relevant for Poison Water mirror matches)
* If player knows Mana Leak, 50% chance for the enemy to use Mana Leak (this is never relevant for any enemy that poses an actual challenge)
Technically I guess it's allowed to rely on these 50% chances, but it feels bad, so I say a run is stable if it doesn't rely on any 50% chances and unstable if it does.
So from lowest to highest level, and for info purposes the story path through the game that each took (affects the items available, which is important because items improve your stats without increasing your levels):
* Dark Wood 64 (White High) (stable)
* Burning Hill 77 (Fearless) (74 possible if unstable allowed)
* Poison Water 79 (White High) (73 possible if unstable allowed)
* Great Sea 81 (White High) (76 possible on Fearless if unstable allowed)
* Chaos Desert 85 (White High) (83 possible if unstable allowed)
* Ice Land 106 (Black High) (98 possible if unstable allowed)
If anyone wants to brainstorm strategies for lowering any of these levels, I would be eager to hear your ideas.
A lot of these are already pretty slim and it's hard to find more levels to remove.
Obviously we can't level any of the defensive bolts and should take as many items as possible, etc.
As an aside, if you were to ask which clans I find the most fun to play, I guess my rank would be Chaos Desert, Burning Hill, Dark Wood, Ice Land, Great Sea, Poison Water.
But that's just a personal playstyle thing.