In the Land of Azurth, the wizard Mondegreen is infamous among magical practitioners, not because he was powerful (though he was) nor for his output of arcane scrolls (though it was prodigious) but because of his habit of misprinting magical sigils and formulae. He seems to have suffered some sort of malady in this regard, perhaps a curse.
A Mondegreen scroll will not contain the traditional version of the spell it appears to catalog at cursory examination. The subtle errors will either effect some aspect of the spell 50% of the time, giving:
1 Advantage to the spell save
2 An increased duration
3 Increased damage (if applicable)
4 Decreased damage (if applicable)
5 A decreased duration
6 Disadvantage to the spell save
The other 50% of the time, it will not work as it should, but rather produce a magical effect from a roll on the Wild Magic Table.
The original version of this post appeared in 2018.