The Cursed Oasis is an unusual dungeon, composed of two overlapping realms. You will be forced to handle exploration and popcorn monsters in unusual ways. Curses play a large part in this dungeon, so characters that rely on resistances, particularly monks, will struggle.
There are ordinarily no subdungeons in this dungeon, but the Smuggler’s Den will still appear if you prep it.
Monsters: Bandits, Dragon Spawn, Animated Armors, Thralls (Poisonous and Mana burn), and Shades
Special Rules: You gain one stack of Cursed whenever you gain a level in this dungeon. This even affects Crusaders, which are otherwise immune to curses. When you have any stacks of Cursed, you will find yourself in the cursed realm.
The normal realm is a very large and open dungeon containing relatively few walls, with an oasis in the center that can only be explored by LEMMISI or BLUDTUPOWA. Monsters include Bandits, Thralls, Animated Armors, and Dragon Spawn. In addition, while exploring, you will sometimes encounter lifedrain by an invisible monster. These are actually the Shades in the cursed realm, which you can walk through in the normal realm.
If you have any stacks of Cursed, you will immediately enter the cursed realm. In the cursed realm, most dungeon features on the ground are not available: glyphs, potions, boosters, shops, unused altars, gold piles, subdungeon stairs. Even the dungeon exit vanishes. Active altars, which remain available, are the only exception. Thus, before fighting a Bandit or gaining a level, you should have a plan for killing enough popcorn to clear your curses if you still need to exploit these resources.
The Shades become tangible in the Cursed Realm and provide a valuable source of XP and Curse-clearing. However, because they can blink into blackspace and then lifesteal again, it is risky to fight higher-level Shades before the dungeon is mostly explored.
The Cursed Realm also features a large number of Erosive Eelroots in the locations of shops, boosters, potions, and gold piles. The dungeon is open enough that they don’t usually interfere with getting around; they are useful to build up extra stacks of Cursed so you can avoid getting kicked out of the Cursed Realm before you want to.
The primary boss of the Cursed Oasis is the Cursed Dragon, the only monster that appears only in the normal realm. He has decent but unremarkable stats: 546 HP, 86 attack, Retaliate: Fireball, and magical attack. Before the Curse Shade is defeated, he also has Curse Bearer, so you won’t be able to easily fight him before you’ve taken care of the second boss.
The secondary boss of the Cursed Oasis is the Curse Shade, who appears only in the cursed realm. He has only 159 HP and 60 attack, but 60% physical and magic resistances. He also has both 40% Lifesteal and Blink, so you won’t be able to carry much if any blackspace between fighting him and the Cursed Dragon. The Cursed Shade drops the Dragon Soul item when slain, which provides a 15% chance to cast spells for free, and forces you into the normal realm even if you have any remaining Curse stacks. You are not obliged to kill the Curse Shade to win the dungeon.
There are two main approaches to winning the Cursed Oasis, depending on whether you want to kill - or avoid - the Curse Shade.
If you want to kill the Curse Shade, you will need to either bypass its resistances, or simply be able to dish out enough damage to grind through its health despite the 60% resistances. Prepping the Really Big Sword helps to avoid most of the Physical Resistance, so it's useful also against the regular Curse Realm shades, however none of the other monsters have Physical Resistance, and being slowed can be a nuisance as it makes killing low-level Thralls non-trivial due to their status afflictions; as well as resulting in an additional curse layer for each Bandit or Erosive Eelroot killed in melee, which can also pile up to undesirable levels. Using Binlor and reducing the Curse Shade's resistances via the Stone Heart boon can also be viable - which also helps build up a bit of Magic Resistance that can come in handy against the Curse Dragon; however, consider that there is only a limited amount of walls available on this level, so you will want to pay as few 'Level Tolls' as possible. It's also possible to just keep hitting the Curse Shade until it dies, as its stats are not too high. In any case, be mindful of the Blink.
If you want to avoid the Curse Shade, you will want to have a reliable way to clear - or avoid - Curse Stacks. The obvious way is to play a Crusader, who is immune to the normal Curse stacks. An alternative is to use The Earthmother's Greenblood boon between strikes, which removes a Curse stack, allowing you to keep hitting the Cursed Dragon as long as you have the Piety to pay for the boons. There is one watchout with the Earthmother - if you use IMAWAL on a monster in the Curse Realm, the resulting stone wall will also exist in the Normal Realm; so pick those Eelroots to petrify that are not on top of things you still need to access like stairs, shops or items you still need to pick up. You may also simply leave lots of low-level monsters and kill one between strikes to clear the curse stacks that way; although if you want to set up for this, keep in mind the Death Protections of Animated Armors, and ideally clear them before the boss fight to allow a kill without health loss. Really enterpreneurial playes may also experiment with chaining PISORF against the Cursed Dragon, if for nothing else than to have an excuse to play a Binlor-worshipping Orc Bloodmage.
Classes recommended for this level will partially depend on the strategy, but on top of the above mentioned Crusader, the Berserker is also a good pick, given his natural edge against Animated Armor and Dragonspawn - as well as the Cursed Dragon boss - due to Magic Resistance. Just make sure you fight these creatures in the Normal Realm, otherwise your resistances will not help.