I had trouble placing in text edits in the Google Drive sheet, so I'm presenting the spell edits here. A few spell descriptions were gotten and developed from their links found in the OP of this topic.
My opinion is it is important to imitate the style and wording conventions found in the published Spell Cards to maintain continuity. As such, many of the card texts below were reverted to that format. However, some of the opening sentences were amended to work in a bit from your added fluff descriptions.
Deluding Spores: "re-roll" >
reroll [The change matches the WoM Future Sight spell. GimmeYerGold had posted a Noxious Spores card
here. I'm not sure if you can pull the art with sufficient resolution or not, but maybe a PM request would get him to provide it.]
Marsh Mists: "This spell creates a concealing fog when cast on any one monster. That monster may then move unseen through spaces that are occupied by Heroes the next time it moves."
Rot: "This spell causes a foul rotting of flesh when cast on any one Hero. Roll 3 Combat Dice. Each skull rolled inflicts one hit. The Hero defends by rolling as many dice as he has Mind Points."
[Other attack spells either include an entity like Vengeful Spirit or something resembling a weapon like Arrows of the Night. Rot feels like neither, (even after dropping the adjacency requirement and red die) so this text avoids the word "attack." Maybe this doesn't matter. Maybe use the art from GimmeYerGold's card, Fever, found
here.]
Summon Basilisk: "This spell summons a Basilisk to do the caster's bidding, which appears on any square adjacent to the caster. The Basilisk may move and attack at once."
[I used Mohawk's later version. Like Goblin-King, I prefer using a new monster that already has a figure and stats provided. Check out another of GimmeYerGold's cards, Summon Basilisk, for potential art
here.]
Tangling Vines: "This spell may be cast to ensnare one Hero in tangling roots and vines. That Hero may not move and rolls one less Combat Die to defend. The spell can be broken on a future turn by the Hero rolling one red die for each of his Body Points. If a 6 is rolled, the spell ends. An adjacent Hero may also roll to end the spell by forfeiting an action."
Venomous Strike: "This spell summons several vipers that immediately strike any one Hero with poisonous bites, then vanish. The Hero must roll one Combat Die immediately and on future turns. If a skull is rolled, the spell inflicts 1 Body Point of damage. The spell is broken if a white shield is rolled or any Body Points are restored through healing."
["Several vipers" was swapped in to account for the art. I thought it better to mention the vipers vanish, as with Spirit of Vengeance.]