You'd gone back to your promotion to Lady Magister, which is certainly a pleasant memory but also your formal introduction to the pocket dimension that the Grey College is entirely ensconced within, which also provides the mechanism for some of the more esoteric spells of Ulgu. Substance of Shadow is the one you know, and somewhere along the way of trying to mentally examine the spell itself for how it might link in to that border plane, some of the syllables of that spell slipped into Mockery of Death.
[...]
"Paper," you say, and Max only hesitates for a second before fishing a notepad out of his pockets and passing it to you with a quill. With haste you jot down the shorthand for the syllabic jumble you'd inadvertently said before it drifts from your mind completely, and take a number of notes on the part where you'd inadvertently blended two syllables together in a way that didn't really translate to letters.