_{This is Part III of a sequence. Other components: The Alchemist’s Grimoire and
The Alchemist’s Cauldron}

Yet once more advised from the attitude of my fantasy self.
The story nor the entrance of the letter are wanted to resolve the puzzle.
Just like earlier than, the story continues however the puzzles are unrelated.

A number of months later…

Today the social gathering and I had woken up, solely to shortly see that Astrid had not come down for breakfast or invited me to make it.
Soon we discovered ourselves at her room, knocking on the door, with no reply.
Eventually I resorted to lockpicking my manner in, however was shocked to see an empty room, the window on the again broad open.

The present principle is that she ditched us and ran away, which is extraordinarily apparent.
Moments like these are after I wish to assume I’m the neatest one right here.
I quickly excused myself from mealtime and headed to the riverbank and attempt to gather my ideas.

“Now why would she depart us? She appeared to no less than take pleasure in my firm…” I contemplated.
But that is after I heard it. Once I began to take a seat down, there was a peculiar crunching sound coming from my gown. I reached into an inside pocket, solely to discover a lock of vivid orange hair – neatly wound and braided – connected to a chunk of parchment. These have been undeniably from Astrid. I’ve met no one else with papyrus this historic, not to mention anybody with this shade of hair.

Here’s what was on the paper:

My expensive buddy,
    Please forgive me for leaving so abruptly. I'm not who you imagine I'm. I've wished to debate it with you for the longest time, however I not too long ago found that you're not the one one snooping by means of my texts.
    I concern that our social gathering members could resent me if they found who I'm. Therefore, I ask you to please maintain this message secret from the others.
    Please don't try to search out or comply with me. It is suicide to take action. I don't want extra blood of my companions filling my footsteps.
    You ought to discover enclosed one thing to recollect me by. It can also aid you survive must you try and comply with me.
 
    Truly,
    Astrid

I discovered this on the opposite facet of the letter:

What is Astrid’s secret?

Errata

The shapes in strains 5 and 13 must be triangles, not squares.

Hint the First

That second D-word would possibly aid you…

Hint the Second

The equation is a key to a fantastic cipher…

Hint the Third

Let’s hope her absence would not depart any lasting harm…

Hint the Fourth

I’d simply need to spell it out…