I exclusively play Hardcore and have 60+ hours. Yada-yada-yada bona fides. Onwards!
I think the best biome to begin with has to be the one that I dare say is everyone's current favorite. The Dungeon is simply fantastic. It hits a very classic and iconic feel with its theme and aesthetics, it has by far the most varied and numerous interactables, it has more Guardians on average on offer, the shops are cooler, the rewards are better, and the encounters are relatively well balanced by being neither too difficult nor too easy, and it has the most interesting encounter maps.
In fact, when I get the Dungeon as my first biome, I know I'm going to have a fun run.
Overall I think my favorite things about the Dungeon can quickly be summarised as:
- Inkadoo(?)s shop offering two Guardians allowing for both a larger pool of initial party members AND to get two party members without having to rely on dice rolls. I really cannot stress how much I dislike having a 3/4 chance to lose out on a crucial gamepiece that the game is balanced around me having.
- The chance to get the coverted mercenary camp shop, which boasts a whooping 4 Guardians for you to pick between in your search for the perfect pair.
- The battlefield hazzards and obstacles allowing for a lot of fun and interesting plays. They really do mix things up in a delightful way while also looking great. I love entering living rooms, libraries and armouries.
- The enemies being a mix of demons and undead help give the place a somehow timeless feel. You really do get that "on a quest"-feeling when you're down there.
- The fact that most rooms have something in them that is useful to you. Even an empty room can have a bookshelf with potential spells or an armour rack with equipment.
- Most key rooms giving you gold instead of dice and satchel cards. Admittedly this is more of an early quirk thing, but currently gold, cards and Guardians are the fun rewards with satchel cards (exeption being artifacts) and dice feeling more like a letdown.
Conversely my least favorite thing is, well... the bosses, really.
Nithsrot Gehr: Nithsrot stands out as being quite possibly the most dangerous and potentially overtuned boss in the game. Being a 5/X with Flying is spooky enough as is, especially if he is your first boss, but the fact that he causes Vulnerable 3 and can steal spells from you even if he hits your allies puts him a fair bit over the top. He is also the only boss in the game who can 1-shot your Summoner, and he does it surprisingly often if he gets the chance (Example: Attack for 5 -> steal Lightning Storm -> Hit you 3 times for 2 -> Trigger Vulnerable 3 times for 9 -> 5+6+9=20). The probably most problematic thing about him being that you cannot circumvent his ability either, as you draw a new hand at the end of your turn so even discarding your hand won't prevent him from potentially stealing, say, a Frog Demon from you.
Recommendation: Remove the Vulnerability 3 from him. Being able to steal cards and having an imposing 5/X body with Flying should be more than enough to make people fear him.
Antarax: Antarax has the exact opposite problem of Nithsrot Gehr in that he is quite possibly the easiest boss in the game. Truth be told, he apparently has the best deck of any boss, but he has to survive a full 2 rounds before he is apparently allowed to cast spells and even then I really haven't found his deck to be all that intimidating. Or at least I haven't seen him pull out any Bloodlusts, Katanas, or Power Overwhelmings. He really just feels like an Elite+ most of the time.
Recommendation: Buffs. Maybe let him cast spells right away, or improve his deck. Antarax really likes +Attack cards, so give him a bunch of those. Make me fear him and his massively boosted 11+ Lifesteal + Pierce.
Overall, I am going to strongly recommend using Dungeon as the benchmark for all the other biomes with a particular emphasis on how keen the map is on offering rewards and how much fun a lot of the encounters tend to be.
If the Fungeons (Eh? Eh? ;3) are the most fun and interesting biome, then the Desert is sadly the least - with a caveat that a lot will disagree with me on - fun one. Being the only map with harsh weather, namely the sandstorm that forces you to sacrifice range entirely is one thing. Marauder encounters that can spawn as early as act 1; pitting you against 4+ 3/5s with armour and knockback/ensnared who take the first turn being another. The arena (that I honestly like) forcing you to fight a gauntlet without a single break in order to earn an incredibly mediocre reward (that helmet isn't even permanent - it goes away when you camp) is an entirely third.
Add in a surprisingly uninteresting number of interactables (just boxes and barrels) and hazzards (just cacti) compared to the dungeon and the potential for quite possibly the hardest common encounter ("Sand Swarm) in the game by far to spawn, and you get the most punishing and unrewarding biome in the game. It is, however, not the least interesting.
Unlike the dungeon I think it is valid to look at some specifics here:
"The Sand swarm": It's, what, 3+ Earth Elementals, 3+ Earth Drakes and 2+ Rock Giants who can spawn on a rather small map with little to no chokepoints, because deser biome. That's a staggering amount of 8+ health enemies who can all cause Vulnerable and therefore stack their damage on top of each other. It is like a meatgrinder, and it is a bit over the top. The dungeon biome has a similar encounter that can spawn with a skeletal horde with a dragon and the desert also has a Dreadnaught army encounter that can spawn, but I will easily put the Sand Swarm as my personal top pick for the most overtuned common fight in the game. It is frankly obscene how much damage it can cause.
Recommendation: Tune it down juuuuust a smidgin. Also consider looking at Vulnerability, because I think you might be undervalueing how powerful it is. Combo has a surprisingly large list of requirements, and Vulnerability is like Combo+ in most cases.
Harsh weather: Not much of a fan of taking damage outside of combat, so sunlight is not really my thing. And while I honestly think that sandstorm's blindness can lead to interesting decisions, the fact that it is entirely one-sided really doesn't feel fun or fair. I don't hate the mechanic, but I believe that it has to be handled differently.
Recommendation: Maybe I'd be more down with it if weather affected both parties with a new keyword (let's say "Coated" for example) being made to denote characters being immune to weather and we were giving spells/minions that interacted with weather?
Marauder parties: As a way to get Guardians I actually rather like it. However, the fact that said party members require dice rolls (grr... :V) does sour the deal a bit. My main issue with them though is that they can spawn in act 1, way before you are ready to take them on, and they both refuse you the first turn and the right to retreat pre-combat.
Recommendation: consider act-restricting them and/or making the freed guardian either guranteed or have improved odds of success. You just saved the plonk from a group of hat-wearing loons while losing all your ressources in the process, they should maybe be a bit more grateful.
The Arena: Again, I like the arena. However, I have also seen a fair bit of complaining about it and, frankly, I see why. Much like Marauder packs it takes away control from you, which is bad enough. But the real kicker is that it makes you fight several battles against increasingly dangerous enemies in a field full of hazzards. Now, of course the gimmick is that you are in a massively advantageous position and can use the traps to beat the silly-billies to death, but it is still a pretty tall order to ask of the average player that they should be able to handle the arena without ever having their ressources restored. LOVE the little ludonarrative with getting a guardian there though. It is cool to get an ally who also helps you catch your breath (albeit with dice rolls :V), very thematic way to find a party member.
Recommendation: Temporarily give the player Scribe 3 while in the arena, or something like that. Let them catch their breath. Alternatively make the arena opt-in and, umm... improve the reward. That helmet is neither good nor permanent.
I think it is worth noting that the Gold Dragon fight can lead to a lot of irritation. Not because it counters certain playstyles, that's how these games work, but because apparently the Gold Dragon spell is a kickstarter reward that most, myself included, will never be able to get, and that is... bothersome.
My favorite thing about the desert is the bosses however, ignoring potential bad-feels caused by the Gold Dragon. Especially the pyramid mini-biome is incredibly cool and I very much do hope we get a full on pyramid biome at some point. With mummies and scorpions and stuff!
The unfortunate thing is that there really isn't a lot to say about the forest biome. It isn't as punishing as the desert, but it also manages to just be kind of... is it rude to say I find it somewhat unremarkable? Having no hazzards to speak of, interactables being largely limited to the trusted barrels and crates, treasure rooms being surprisingly annoying to deal with - although they do have spellbooks and armour racks in them which is cool, and an aesthetic that lacks a certain sense of personality.
Really, the most noteworthy thing about the forest biome is Rabbitus, and we all like Rabbitus. Rabbitus is just fun and cool. Love him. I guess Treeant is fun too. Yeah, I like Treeant a lot. The bosses are pretty neat as well. Oh, and I like the little underground area. And Birthday Boy! Actually, come to think of it, it seems to me like the most noteworthy things about the biome isn't the biome itself, but rather a small number of characters within it, and I don't think that is entirely a good thing.
The weird thing is that in the duels mode you can get forest themed maps full of thorny vines and exploding plants, and those are incredibly cool and fun. Personally I'd consider adding in more, well, variation to the biome. Especially hazards. I like hazards.
Now Chumsie go sleepsie. Sorry for trailing off a bit in the end, it is late here.