I'm not certain about most of these--most of the bottom text appears to be more in the vein of a Dungeon Master's introduction or response than a specific historical note. However, locations at least can be found that correlate to each description.
The largest, most magical desert in the Forgotten Realms, the Anauroch is a good candidate for a location filled with an alien magic. This fits with its historical masters, the Phaerimm, which were aberrant spellcasters sealed in a cavern beneath the desert behind the Sharn Wall. While the Sharn Wall was reported to be silver, the art description for this card might have been something like "Mystical barrier in desert caverns, camp below" and here's what they got.
This is by far the clearest of the cards. Storm King's Thunder has an entire chapter in the storm giant citadel of Maelstrom, an underwater fortress at the bottom of a violent whirlpool.
Swamp: Ched Nasad?
Again, a guess, but the firebombed, ragged-webbed drow city of Ched Nasad is an excellent candidate for this swamp, yet more so because the people who destroyed it were dark dwarves and thus unlikely to have communicated with the surface races about its destruction.
Axeholm, as it is recorded in Dragon of Icespire Peak, is a ruined dwarven city containing a number of ghouls and a banshee. While there is no specific basis for drums, there is specific evidence for Axeholm being haunted and long abandoned, so this is my best guess.
Cormanthor is an ancient elven forest that was, in 1357 DR, attacked and damaged by Moander, the long-assumed-dead god of rot and decay. This card could be set in the early days of the attack before the elves knew Moander had escaped.