Here is an idea for an outdoor and indoor area, including some monster ideas:
Deep in the midnight grove, despair shadows the land in silent fetter where once pixies frolicked and fauns capered amidst the first world’s eternal summer. The Aetherial’s twisting, consuming advance throughout Cairn is not sated on reality alone, but also on Carin’s myths and legends, dreams and hopes, and fears and loathings. Corrupting the faery realms is sweet nectar for the Aetherial’s parched souls, who take perverse rapture in despoiling the purer things, in cloaking beauty with nightmare visage.
Outside Areas:
As the character walks into a large copse of trees alight with iridescent butterflies, the daylight dims and the shadows lengthen, while the flora begins to take on a pallid glow. The area is completely silent; there is no sound or music in this area. Walking around the copse keeps the character in their current area. The further the character walks in, the more the pallid glow increases until they pass by dark standing stones and are surrounded by enormous plants glowing eerily and swaying to the whims of an unfelt breeze. Once they enter the area they are greeted by tainted will-o’-wisps and warpfire fauns, who now only delight in slaughter. Further in, twisted trees tower over fields of dead grass and wild flowers, shrouding clearings where the now macabre dance of the faeries languishes. The realm is situated around a great mound, where the faery court makes their home.
For example, take a gorgeous outside area like Outer Mongolia in TQ, or the first area of Trine 2, super-saturate it to make it more than alive (but not tacky), and then corrupt and warp it with grimpunk flavor. Enough beauty needs to remain to make the loss impactful. This area could also serve as a counterpoint to the bleak twilight of the rest of the world.
Inside Areas:
Hidden in the darkest recesses of the twisted wood under a hill of dying heather and broken stone, the once musical halls of the faery queen are now a grim, overgrown abode of beautiful ruin. The majestic halls now wander in impossible ways creating endless spirals descending to nowhere; floors that become walls and then ceilings, only to become floors once again with the character never loosing their footing, twist through star fields; galleries that bend in on themselves so that the character sees themselves walking to where they currently are standing; and so on.
Every hall used to lead to the queen’s throne like spokes in a great wheel, but now each is more likely to lead to flesh-eating bramble mazes infested with redcaps, or malignant gardens swarming with death’s-head pixies, than the music rooms, fountains, or courtyards that once brought joy to the formerly untainted denizens. Different entrances lead to cut-off parts of the queen’s halls, each with a warped champion faery holding court in rebellion against their queen. In the deepest hall, the queen still seeks to rule over her discordant realm with malice and wrath.
Creature Ideas:
Warpfire Fauns – Skeletal fauns burning with the lurid flames of the Aetherial warp. Peltasts, trappers (who throw gossamer nets), and shaman would all fit, and would be complimented by warped special abilities. (Yes, this is a shameless way to get TQ’s Satyrs mixed with Liche Kings into the game)
Death’s-head Pixies – Iridescent, skull-winged faeries with a penchant for poison and turning your pets against you.
Warpblight Blossoms – Gargantuan flowers infused with warpfire and surrounded by a cloud of caustic pollen, they shoot burning seeds at any non-Aetherial that comes too close.
Nightwood Dryads – Beautiful maidens who attack from their oaks with root and branch attacks until their tree is nearly dead, when they fly out in whirlwind fury to destroy any foolish enough not to flee.
Will O’ Wisps – Tainted by putrid warpfire, these floating lights now glow in sickly shades seeking to consume the unfortunate lost with their burning touch.
Shadow Brother Spriggans – Ugly mottled-gray faeries that attack from the shadows with jagged knives. Wingless, they grow in size and power as they take damage.
Burning Banshees – The only sound you ever hear in the grove may well be your last. Possible sub-bosses, they appear as ethereal maidens whose screams disrupt skills and drains life, while healing themselves. A banshee becomes brighter and more solid as she feeds off of the horror her scream brings.
Redcaps – These buggers might not need much warping; they appear as scrawny old men draped in rags, missing more than a few teeth, and with patches of wiry hair sprouting from under their bloody caps. They attack with oversized scythes that deal oversized damage, which also grant them surprising reach and cause copious amounts of bleeding. When in close, they attack with spiked boots to a character’s mid-region.
Boss Ideas:
Mab the Faery Queen – Brooding in a throne room deep in the vaulted Faery halls, Mab flutters jerkily through the air on eight broken butterfly wings around the fabled first tree, the one thing in her realm that withstood the Aetherian attack untainted. The once vibrant mosaic of trees and flowers that surround her hall have begun to dissolve, melted by warpfire so they ooze down like rotten wax into rainbow pools, slowing all who tread in these once idyllic halls (think Robin Williams walking in the painting in ‘What Dreams May Come’ for a visual of how the hall looks). Mab attacks with thorns and thistle in great arcs, calling Aetherial fiends from the dying color spilling throughout her once perfect domain.
Master of the Hunt – A proud hunter clad in ethereal green towers over his pack of spectral hounds, who howl soundlessly at an unseen moon. With a thrust of his spear, he sends his hounds at their new quarry – you. The legendary huntsman has not escaped the Aetherial assault and now hunts for his new masters, reveling in the burning power coursing through him. Master of the spear both at range and in melee, he can call back any of his fallen hounds with the peal of his silent horn.