I'm at a loss as to what to do; I have the Sigil stone, and nothing unusual happened inside the Oblivion gate. There were still some Daedra outside the gate however, before I entered, but killing them all afterwards didn't seem to do anything. I tried loading a save before closing the gate, but that didn't help :/
I'm left to think this may be mod-related, so I'm posting this here. Here's my current load list, I have no other weather mods loaded up except All Natural 1.1, which always worked well for me.
Spoiler
Oblivion.esm
TR_OoT_Main.esm
You Are Here.esm
All Natural Base.esm
Francesco's Leveled Creatures-Items Mod.esm
Cobl Main.esm
Mart's Monster Mod.esm
CM Partners.esm
Easy_Companion_Share.esm
Younger Hotter NPC's v1.0.esp
Unofficial Oblivion Patch.esp
DLCShiveringIsles.esp
Unofficial Shivering Isles Patch.esp
LoadingScreens.esp
LoadingScreensAddOn.esp
LoadingScreensSI.esp
Natural Selection.esp
Natural_Habitat_by_Max_Tael.esp
All Natural - Real Lights.esp
All Natural.esp
All Natural - SI.esp
AliveWaters.esp
AliveWaters - Koi Addon.esp
AliveWaters - Slaughterfish Addon.esp
Ayleid Loot EXtension.esp
Fatality Cam.esp
P1DseeYouSleep.esp
Purge Cell Buffers - Loading.esp
SI Living Economy.esp
DLCHorseArmor.esp
DLCOrrery.esp
DLCVileLair.esp
DLCMehrunesRazor.esp
AyleidMeteorIronWeaponsBASE.esp
AlternativeLightArmors12.esp
Battledress.esp
ClassyClothingCompendium.esp
DaedricCrescentBlade.esp
LootableLichHelm_Hvy.esp
Rogue Sun's Blood Lust Dress.esp
SickleIrons_RT.esp
SilverwareWeapons.esp
VA_DaedricPriestessArmour.esp
Wyrmfang.esp
LeatherHunterArmour.esp
Daedric Lord Armor.esp
DLCThievesDen.esp
Francesco's Optional Leveled Quests.esp
Francesco's Optional Leveled Arena.esp
Francesco's Optional Files 2.esp
Cobl Si.esp
Mart's Monster Mod for Fran.esp
Mart's Monster Mod - Additional Enemy NPC Vars.esp
Mart's Monster Mod - Gems & Gem Dust.esp
Mart's Monster Mod - Hunting & Crafting.esp
Mart's Monster Mod - Durability & Damage.esp
Mart's Monster Mod - Fran's leveled quests.esp
Mart's Monster Mod - Safer Quest Locations.esp
Mart's Monster Mod - Dungeons of MMM.esp
Mart's Monster Mod - More Wilderness Life.esp
Mart's Monster Mod - City Defences.esp
Mart's Monster Mod - Extra Wounding.esp
Mart's Monster Mod - Farm Animals.esp
Ivellon.esp
adTreeHome.esp
AyleidArrows.esp
CDEP_FanaCeya.esp
Fort Baltsine.esp
Gaenor in Dementia.esp
OldCrowInn.esp
RuinsOfBrenfa.esp
Spear_of_Bitter_Mercy.esp
sunk ships.esp
The Ayleid Steps.esp
TR_Stirk.esp
Torynwyll.esp
VOILA - Soldiers of Empire.esp
DLCFrostcrag.esp
Knights.esp
The Lost Spires.esp
ElsweyrAnequina.esp
Feldscar.esp
Faregyl.esp
xuldarkforest.esp
xulStendarrValley.esp
xulTheHeath.esp
MMMMWL-TheHeath patch.esp
XulEntiusGorge.esp
xulFallenleafEverglade.esp
LostSpires-Everglade patch.esp
Anequina-Fallenleaf-Patch.esp
xulColovianHighlands_EV.esp
xulBeachesOfCyrodiilLostCoast.esp
xulBravilBarrowfields.esp
xulAncientRedwoods.esp
xulCloudtopMountains.esp
xulBrenaRiverRavine.esp
xulImperialIsle.esp
xulAspenWood.esp
Natural_Vegetation_by_Max_Tael.esp
Harvest [Flora].esp
Harvest [Flora] - DLCFrostcrag.esp
Bag of Holding.esp
Cliff_BetterLetters.esp
Cliff's Shacks Basemants-Radiant AI.esp
DS Less Predictable Respawn.esp
fadingtorches v1.3b.esp
M.O.E. - Travel Services.esp
M.O.E. - Lycanthropy and Lichcraft.esp
P1DkeyChain.esp
persuasioncompatable1.8.esp
Salmo the Baker, Cobl.esp
Quest Award Leveller.esp
Quest Award Leveller - Vile Lair.esp
RealisticForceMedium.esp
SetEssentialActors.esp
SupremeMagicka.esp
SM_ShiveringIsles.esp
MidasSpells.esp
Syc_AtHomeAlchemy.esp
attack and hide medium v2.1.esp
Deadlier Traps.esp
sycHearNoEvil.esp
sycSHOUT.esp
Enhanced Grabbing.esp
SamVimes's Feint Death.esp
actors_in_charge.esp
_darker_dungeons.esp
Luchaire's Dryad Race for MMM.esp
CM Partners.esp
CM Partners Extra NPCs.esp
ArianaTrudeaux.esp
_burning_kvatch.esp
Francesco's 10 days respawn time - 1-20 day lenght rescale.esp
SPAWN.esp
Get Wet - just droplets.esp
Capucine'sEyeSelection.esp
Nightshade_Armor_ConflictFree.esp
Alkwynd.esp
Streetvendors.esp
Sunken Chapel.esp
RTBlackEveningDress.esp
kdRhazed.esp
PTFallingStars.esp
DADryadWilla.esp
DarknessHollows.esp
BFG's Enhanced Armory.esp
Phitt's Phighting Phixes.esp
Creature Damage Fix.esp
Weapon Expansion Pack for Oblivion Nthusiasts.esp
Bashed Patch, 0.esp
TR_OoT_Main.esm
You Are Here.esm
All Natural Base.esm
Francesco's Leveled Creatures-Items Mod.esm
Cobl Main.esm
Mart's Monster Mod.esm
CM Partners.esm
Easy_Companion_Share.esm
Younger Hotter NPC's v1.0.esp
Unofficial Oblivion Patch.esp
DLCShiveringIsles.esp
Unofficial Shivering Isles Patch.esp
LoadingScreens.esp
LoadingScreensAddOn.esp
LoadingScreensSI.esp
Natural Selection.esp
Natural_Habitat_by_Max_Tael.esp
All Natural - Real Lights.esp
All Natural.esp
All Natural - SI.esp
AliveWaters.esp
AliveWaters - Koi Addon.esp
AliveWaters - Slaughterfish Addon.esp
Ayleid Loot EXtension.esp
Fatality Cam.esp
P1DseeYouSleep.esp
Purge Cell Buffers - Loading.esp
SI Living Economy.esp
DLCHorseArmor.esp
DLCOrrery.esp
DLCVileLair.esp
DLCMehrunesRazor.esp
AyleidMeteorIronWeaponsBASE.esp
AlternativeLightArmors12.esp
Battledress.esp
ClassyClothingCompendium.esp
DaedricCrescentBlade.esp
LootableLichHelm_Hvy.esp
Rogue Sun's Blood Lust Dress.esp
SickleIrons_RT.esp
SilverwareWeapons.esp
VA_DaedricPriestessArmour.esp
Wyrmfang.esp
LeatherHunterArmour.esp
Daedric Lord Armor.esp
DLCThievesDen.esp
Francesco's Optional Leveled Quests.esp
Francesco's Optional Leveled Arena.esp
Francesco's Optional Files 2.esp
Cobl Si.esp
Mart's Monster Mod for Fran.esp
Mart's Monster Mod - Additional Enemy NPC Vars.esp
Mart's Monster Mod - Gems & Gem Dust.esp
Mart's Monster Mod - Hunting & Crafting.esp
Mart's Monster Mod - Durability & Damage.esp
Mart's Monster Mod - Fran's leveled quests.esp
Mart's Monster Mod - Safer Quest Locations.esp
Mart's Monster Mod - Dungeons of MMM.esp
Mart's Monster Mod - More Wilderness Life.esp
Mart's Monster Mod - City Defences.esp
Mart's Monster Mod - Extra Wounding.esp
Mart's Monster Mod - Farm Animals.esp
Ivellon.esp
adTreeHome.esp
AyleidArrows.esp
CDEP_FanaCeya.esp
Fort Baltsine.esp
Gaenor in Dementia.esp
OldCrowInn.esp
RuinsOfBrenfa.esp
Spear_of_Bitter_Mercy.esp
sunk ships.esp
The Ayleid Steps.esp
TR_Stirk.esp
Torynwyll.esp
VOILA - Soldiers of Empire.esp
DLCFrostcrag.esp
Knights.esp
The Lost Spires.esp
ElsweyrAnequina.esp
Feldscar.esp
Faregyl.esp
xuldarkforest.esp
xulStendarrValley.esp
xulTheHeath.esp
MMMMWL-TheHeath patch.esp
XulEntiusGorge.esp
xulFallenleafEverglade.esp
LostSpires-Everglade patch.esp
Anequina-Fallenleaf-Patch.esp
xulColovianHighlands_EV.esp
xulBeachesOfCyrodiilLostCoast.esp
xulBravilBarrowfields.esp
xulAncientRedwoods.esp
xulCloudtopMountains.esp
xulBrenaRiverRavine.esp
xulImperialIsle.esp
xulAspenWood.esp
Natural_Vegetation_by_Max_Tael.esp
Harvest [Flora].esp
Harvest [Flora] - DLCFrostcrag.esp
Bag of Holding.esp
Cliff_BetterLetters.esp
Cliff's Shacks Basemants-Radiant AI.esp
DS Less Predictable Respawn.esp
fadingtorches v1.3b.esp
M.O.E. - Travel Services.esp
M.O.E. - Lycanthropy and Lichcraft.esp
P1DkeyChain.esp
persuasioncompatable1.8.esp
Salmo the Baker, Cobl.esp
Quest Award Leveller.esp
Quest Award Leveller - Vile Lair.esp
RealisticForceMedium.esp
SetEssentialActors.esp
SupremeMagicka.esp
SM_ShiveringIsles.esp
MidasSpells.esp
Syc_AtHomeAlchemy.esp
attack and hide medium v2.1.esp
Deadlier Traps.esp
sycHearNoEvil.esp
sycSHOUT.esp
Enhanced Grabbing.esp
SamVimes's Feint Death.esp
actors_in_charge.esp
_darker_dungeons.esp
Luchaire's Dryad Race for MMM.esp
CM Partners.esp
CM Partners Extra NPCs.esp
ArianaTrudeaux.esp
_burning_kvatch.esp
Francesco's 10 days respawn time - 1-20 day lenght rescale.esp
SPAWN.esp
Get Wet - just droplets.esp
Capucine'sEyeSelection.esp
Nightshade_Armor_ConflictFree.esp
Alkwynd.esp
Streetvendors.esp
Sunken Chapel.esp
RTBlackEveningDress.esp
kdRhazed.esp
PTFallingStars.esp
DADryadWilla.esp
DarknessHollows.esp
BFG's Enhanced Armory.esp
Phitt's Phighting Phixes.esp
Creature Damage Fix.esp
Weapon Expansion Pack for Oblivion Nthusiasts.esp
Bashed Patch, 0.esp