Hard (for me, the mostly IOTM-less player. I do have a bunch of skills, but they don't seem to be helpful yet. I should have gone sauceror to reduce the pain)
Everywhere is flooded. Instead of fighting normal bosses, you fight water clones of them which are more powerful. Of course, water clones suck - anyone who has fought Demyx in Kingdom Hearts knows that. Bosses seem to have damage caps, and apparently can do things like remove buffs.
There is a depth rating everywhere due to flooding. Underground = more flooded. More depth = harder.
You fight some wandering monsters which can give fishbones, which give access to a shop that has helpful items, or potions, or access to the thunder skills. You have to fight a wandering monster at depth 6 to access the skills. Outside, inside and underground areas give different skills. I think... that you must use the special skills or the correct monster will not appear.
depth 1 - 1 fishbone
depth 2 - potion + 50% initiative, 40 adv
depth 3 - 2 fishbones
depth 4 - potion - reduces item loss, 40 adv
depth 5 - 3 fishbones
For the fishbones, I like the facemask (-30ML), as it frees up some of my accessory slots. I also have the fins (enemies don't hit as much), and want to get the corset (lowers water level).
Depth 6 underground - menagerie
Depth 6 underground (with thundercloud) - inside cobb's knob, cobb's knob labs
Depth 6 inside (with personal thundercloud) - spookyraven
Depth 6 outside (with thundercloud and rain in loathing effects) - highlands, pirate cove undisguised
Oddly, my records indicate that I got a thunder thigh in the haunted bathroom. I think I was at depth 6, but not due to thundercloud, as that was the second skill I got.
depth 6, underground = tardigrade -> thunder skills
depth 6, inside, with thundercloud = aquaconda -> rain skills (I guess you need a cloud to get rain)
depth 6, outside, with thundercloud and the rain in loathing = storm cow -> lightning skills
Depth Levels: (without depth increasers/decreasers)
cobb's knob first two levels - 5
cobb's knob menagerie - 6
spookyraven - first floor 3, second floor 4
highlands - 2
pirates - 2
barr - 4
In order to get certain areas to depth 6, you have to use a skill. The progression is thunder -> rain -> lightning. By the way, make sure to remove your depth reducers if you're going for a skill item.
Getting rain skills:
So what I did was use the thunder skill Personal Thundercloud -> 100 turns
I went to the indoor zone the Haunted Bedroom, which becomes depth 6 due to the thundercloud.
fought an aquaconda
Rain skills unlocked!
Thunder - adventure in an underground area at 6 depth, get a thigh from a tardigrade
regeneration - every ~ 10 adventures, you get 30 db, or 50 db with thunder thighs.
Thunder Clap
banish for 40 turns
Thundercloud
increases depth by 2
Thunder Bird
deleveller
Thunderheart
Max HP + 100%
Thunderstrike
Stun
Thunder Down Underwear
summon underwear (disappears after rollover)
Damage Absorption +100
Maximum HP +100
Regenerate 10-20 HP per adventure
Thunder Thighs
more thunder regeneration
Rain - adventure in a depth 6 inside area (example, spookyraven 2nd floor), get a brain from an aquaconda
every 7 adventures, you get 7 raindrops.
Rain Man
noncombat, copier for monsters that are copyable that have been encountered in a Heavy Rains run.
Rainy Day
increases depth by 2
Make it Rain
+300% meat drops combat skill
Rain Dance
100 adv, +20% Item Drops from Monsters
Rainbow
prismatic damage combat skill
Rain Coat
shirt (disappears after rollover)
So-So Resistance to All Elements (+2)
+10% Item Drops from Monsters
Combat Initiative +40%
Rain Delay
passive +3 all res
Lightning - adventure in a depth 6 area, outside, fight a storm cow, drops lightning milk - recommended to use up MP to below 50 so it doesn't drain as much HP, and raise HP
Lightning Strike
insta kill, items drop
Clean-Hair Lightning
max MP + 100%
Ball Lightning
yellow ray, 100 turn cooldown
Sheet Lightning
spell damage + 100%, damages attackers
Lightning Bolt
5000 damage on 3rd use in combat
Lightning Rod
summons a staff (disappears after rollover)
Spell Damage +200%
Maximum MP +50
Regenerate 5-10 MP per adventure
Riding the Lightning
Maximum MP +100%
It seems you can keep at least one skill per ascension. It's unknown at the time how many maximum you can keep, but according to the forum, it's likely to be 3 per skill tree.
Due to flooding, items may wash away (even if it is yellow rayed). You can equip a pool skimmer from the mall to catch other player's lost items. There are some junk accounts to ensure that you will get something, I guess in case it happened that were no other players around who had lost something. There are also water wings in the mall to reduce the painfulness of this path, by reducing the ML, and also an umbrella to reduce depth. Throw away your pride and use the wings, if you must.
The reward is an item giving a skill that deals prismatic damage. It looks like you get an extra 1 damage per item used, which seems kinda weak? The cap is 11, so 55 damage total. I'm selling my lone beautiful rainbow.