The Wrath of the Immortals sees the formation of the Great Crater. You might finger wavey those events as 'hey its good because the immortals fixed it' but in the real world those events would have been truely destructive.
The description in AC1010 Poor Wizards Almanac indicates that the crater is over twenty miles in diameter bordering the Principality of Blackhill. It is on the border between Glantri and Darokin and is considered close enough to the Broken Lands to be an extension of them.
The Asteroid Impactor itself is described as a Meteorite so we can call it as Iron.
1. Crater over twenty miles in diameter.
2. Iron Meteorite.
To create this twenty mile diameter crater a meteorite of iron would be 6000' in diameter impacting at an angle of 38 degrees, the immortals having knocked it off course from Darokin into Southern Glantri.
The final crater is twenty one miles in diameter and two thousand eight hundred feet deep.
While the crater might be over twenty miles in diameter (an area encompassing seven 8-mile hexes) the impact throws up twenty cubic miles of rock burying the keeps at Silverston, Soth-Kabree, and Nathrat. The structures are most certainly destroyed but the deep, bunker like dungeons might survive.
There are boulders in this crater rim material that are a thousand feet in diameter to two hundred and twenty feet in diameter out to the twenty eight mile boundary.
The quake is 8.6 in magnitude. At three hundred miles it shakes buildings without damage. It shakes buildings in Shireton waking the residents.
The Fireball is nineteen miles in diameter.
The Thermal Radiation causes third degree burns (3d6 damage) out past two hundred and fifty miles radius and first degree burns (1d6 damage) out at three hundred miles radius to people and animals. The western edge of Alfhiem forest ignites and begins burning. The Grass and crops of Darokin burns as do the grasslands in western edge of the Khanate.
The Wind Blast
At the crater's edge there is a wind blast headed outward. Here it is over five thousand miles an hour.
At sixty miles where the boulders falling from the sky are now eight feet in diameter an airblast of one thousand three hundred and ninety miles an hour hits a few minutes after the asteroid impact blowing away even stone buildings.
At a hundred miles the debris is two feet in diameter and the Air blast is just over seven hundred miles an hour.
At two hundred miles the debris is a mix of two and a half inch gravel and sand. The Air blast has reduced to a cyclonic wind gust of around two hundred and fourty four miles an hour. Wooden buildings are blown away and ninety percent of the trees are blown down.
At two hundred and fifty miles the ejecta material is gravel and fine sand. Wooden buildings have collapsed as a one hundred and seventy mile an hour wind gust hits.
At three hundred miles ejecta is a fine gravel and dusty sand and thirty percent of trees are downed as a hundred and twenty seven mile an hour wind blast reaches the mountains above the Five Shires.
The Five Shires are spared. Those halflings exposed suffered sunburn.
The fire in western Alfhiem has spred to ignite the whole forest fed by cyclonic winds.
Those humanoids not deep in lower broken lands are dead and the landscape has been blown away.
The timber buildings, wizard spellbooks, trees in the City of Glantri caught fire only to be blown away by wind gusts. The populace not in stone fortresses as far north as Fort Nordling are blown away.
While most of Boldavia takes minimum damage from the wind gust with gravel raining from the sky it's Vampire population at Igorov take an unexpected dose of heavy sunburn and cyclonic winds with a clear view of the fireball.
The grasslands of the Taijits in the western khanate ignite and burn totally along with herds and people only to be blown away by cyclonic winds.
Huge boulders and debris come over the silver sierras impacting in lake Amsorak. Ships on the lake ignite and burn. The cities of Akesoli, Akorros, and Darokin begin burning only to be blown away by the wind gust. Selenica, Tenobar, and Athenos survive with little or no damage. The city of Sind likely survived with some damage.
What survivors exist in northern Glantri emerge from their fortresses to find their peasant population, crops and herds gone.
The humanoids of the lower broken lands eventually emerge to find a greatly altered landscape. The broken lands now occupy a vast area of southern Glantri. The surface is scoured of people, soil, plants, animals, and buildings.
Glantri, Alfhiem, Broken Lands, Darokin (and the Cavern of Perpetual Rain in western shadow elf lands is breached by the crater so yeah... These places are gone after the formation of the Great Crater. Given the destructive nature the shadow elf realms and lower broken lands would have subsided.
So...yay the Immortals fixed it.