(It’s a strange letter. It’s more or less completely illegible…)
(But, if you squint your eyes, and, you squint your heart… For some reason, you feel you could understand it)
WELL,
HAPPY NEW YEAR!
OR, WAS IT THE OLD YEAR.
WELL,
IN ANY CASE,
HOW IS DELTA RUNE?
AS YOU ARE WAITING PATIENTLY, THE TIME IS GOING AROUND.
THERE WAS EVEN A RUMOR OF “VALENTINE’S DAY”.
HOW ABSURD.
EVERY DAY IS A DAY OF LOVE,
IF ONLY YOU BELIEVE IT SO.
DO YOU BELIEVE IT SO?
…
SO, THE PURPOSE OF THE MESSAGE.
I WANT TO HELP!
YES, THERE WAS SOMEONE I WANTED TO HELP.
…
I SEEM TO HAVE FORGOTTEN WHO…
YES, IT’S QUITE IRONIC, BUT I SEEM TO HAVE FORGOTTEN.
WAS IT MYSELF? NO…
WELL, PERHAPS.
REGARDLESS, WHEN I SEE THEM, I’M CERTAIN I WILL KNOW IT STRAIGHT AWAY.
I NEVER FORGET SOMEONE I DON’T REMEMBER.
WILL YOU HELP ME?
…
…
YOU ARE VERY ODD, RESPONDING OUT LOUD TO A LETTER.
BUT, YOU SEEM RELIABLE.
I WILL BE COUNTING ON YOU.
NOW, PUT ON YOUR COAT AND WASH YOUR FACE!
OR, PUT ON YOUR FACE AND WASH YOUR COAT.
NOT NECESSARILY IN THAT ORDER.
OR, IN ANY ORDER AT ALL.
GOOD BY!
(There was a sound like something walking away
And, the letter was gone.)
⠀
⠀
This character seems to be an embodiment of corrupted/damaged/etc. code.
Note how this nameless character uses the word "LOVE," which stands for "Level of Violence" in Undertale.
I'm not going to bother listing all the quotes by Spamton that use the phrase [Hyperlink Blocked], but it's pretty clear to me that it means "LOVE." Here, here's an edited quote from him from the Chapter 2 Weird Route:
"I GAVE YOU MY [Commemorative Ring] FOR THE PRICE OF [My Favorite Year]!
AND THIS IS HOW YOU [Repay] ME!? TREATING ME LIKE [DLC]!?
NO, I GET IT! IT'S YOU AND THAT [Hochi Mama]!
YOU'VE BEEN [Making], HAVEN'T YOU!
YOU'VE BEEN MAKING [LOVE]!"
This indicates to me that this character (who is probably not Gaster, given the massive difference in their speech patterns in Japanese) and Spamton may have met. Gaining "LOVE" might be the way to reaching Dess.