Puzzle - Crests

Starting on 5/9, several members of the D&D online community and various staff from gaming news sites began to report receiving keys containing images of a crest and a letter using the glyph alphabet with instructions.

On 5/22, the Immortal Fortress Twitter account added a color scheme for the schools of magic..."While not all mages sort the schools into chromatic scales, it doth appear this train of thought’s the next step on our trail. #NoStoneUnturned - @immortal4tress, 5/22 @ 2:14PM" This clue was used in combination with the crests - specifically, the symbol at the bottom of each piece - for the Spell List Puzzle.

First Crest
Left part provided by Matthew Mercer (voice actor, DM of Critical Role), decodes to the letters "T" and "E" - 5/10 @ 5:18PM


 * A duplicate of the left piece was also posted by Jared Knabenbauer (YouTube gamer) - 5/23 @ 8:25PM

Middle part provided by Allen Hammack (legendary RPG author, associate of Gary Gygax), decodes to "G" - 5/22 @ 10:16PM


 * A duplicate of the center piece was also posted by Joe Manganiello (actor, D&D personality, part of Jocks Machina) - 5/23 @ 11:20PM

Right part provided by Ivan Van Norman (Geek & Sundry staff), decodes to the letter "F" - 5/9 @ 9:04PM

Second Crest
Left part provided by Mike Martin (YouTube podcaster and streamer), decodes to the letters "T" and "F" - 5/24 @ 10:55PM

Center part provided by Nate (WASD20) (D&D YouTube streamer), decodes to the letter "X" - 5/11@ 3:59PM


 * A duplicate of the center piece was also posted by Rhykker (YouTube streamer) - 5/25 @ 5:35PM

Right part provided by C. Edward Stewart ([citation needed]), decodes to the letter "G" - 5/18 @ 4:00PM

Third Crest
Left part provided by Kelly Knox (Geek & Sundry writer), decodes to the letters "G" and "E" - 5/11 @ 7:16PM


 * A duplicate of the left piece was also posted by Taliesin Jaffe (voice actor, "Mollymauk" on Critical Role) - 5/15 @ 5:42PM

Center part provided by Charlie Hall (senior reporter at Polygon), decodes to the letter "O" - 5/11 @ 7:16PM


 * A duplicate of the center piece was also posted by Matt Colville (well known D&D personality) - 5/12 @ 1:52PM

Right part provided by Dan Telfer (DM of Nerd Poker podcast, MAD Magazine Senior Editor), decodes to the letter "F" - 5/12 @ 7:09PM

Fourth Crest
Left part provided by DawnforgedCast (YouTube streamer), decodes to "V" and "C" - 5/14 @ 7:36PM


 * A duplicate of the left piece was also posted by Sam Machkovech (writer for Ars Technica) - 5/20 @ 5:59PM

Center part provided by Gavin Sheehan (writer for Bleeding Cool), decodes to the letter "K" - 5/11 @ 8:33PM


 * A duplicate of the center piece was also posted by Draxx (YouTuber and Twitch streamer) - 5/12 @ 2:06PM

Right part provided by HOLLYWOOKIEE.COM, decodes to "D" - 5/22 @ 10:22AM

Fifth Crest
Left part provided by Utkarsh Ambudkar (Hitch on Force Grey: Lost City of Omu stream) decodes to the letters "A" and "X" - 5/12 @1:06PM

Center part provided by Kimberly Hidalgo (well known D&D personality) decodes to the letter "R" - 5/12 @1:06PM

Right part provided by TrumpSC (Twitch streamer) decodes to the letter "B" - 5/14 @9:31PM

Sixth Crest
Left part provided by Mark Hulmes (DM of the High Rollers D&D stream) decodes to the letters "R" and "F" - 5/26 @1:24PM

Center part provided by DivingRhino (writer for GeekDad), decodes to the letter "V" - 5/13 @ 12:11AM

Right part provided by Gareth Branwyn (writer/editor), decodes to the letter "D" - 5/14 @ 10:33PM


 * A duplicate of the right piece was also posted by Chris Funk (musician for The Decemberists, game designer) - 5/15 @ 9:28
 * Crest Composite6-1.jpg

Seventh Crest
Existence of a 7th crest was revealed on 5/15.

Left part provided by Cig Neutron (player on Inkwell Society stream), decodes to the letters "J" and "B" - 5/22 @ 5:08PM

Center part provided by Holly Conrad (D&D streamer), decodes to the letter "P" - 5/15 @ 9:25PM

Right part provided by Satine Phoenix (WotC community manager, DM of Sirens of the Realm stream, player on Inkwell Society stream), decodes to the letter "C" - 5/16 @ 12:50PM

Eighth Crest
Left part provided by Ruty Rutenberg (DM of Inkwell Society stream), decodes to the letters "K" and "E" - 5/12 @ 1:06PM

Center part provided by Adam Badford (D&D Beyond product director), decodes to the letter "Z" - 5/21 @ 11:58AM

Right part provided by Bill Cavalier (a.k.a. The Dungeon Bastard, a.k.a. actor Tom Lommel), decodes to the letter "A" - 5/16 @ 8:15PM

Solution
The fact that these crests translate to a page/word/letter was suggested in the Keyed Cypher Puzzle.

It was also suggested that this referenced the eight Volo's guides that have been published (seven for D&D 3rd Edition, and one - Volo's Guide to Monsters - for 5th Edition).

If these eight guides are ordered alphabetically, they are as follows: If the eight crests are ordered by the colors of the spectrum (first 6), then black and white at the end, and those crests are mapped to the above order, and the letters are mapped to their numerical equivalents, they reveal eight letters: Putting all those together reveals the letters "ICAOHUFP".
 * Volo's Guide to All Things Magical
 * Volo's Guide to Baldur's Gate 2
 * Volo's Guide to Cormyr
 * Volo's Guide to Monsters
 * Volo's Guide to The Daelands
 * Volo's Guide to The North
 * Volo's Guide to The Sword Coast
 * Volo's Guide to Waterdeep
 * Red: Page 115, word 26, letter 1 of Volo's Guide to All Things Magical = "I" ("into")
 * Orange: Page 75, word 15, letter 6 of Volo's Guide to Baldur's Gate = "C" ("particularly")
 * Yellow: Page 206, word 24, letter 7 of Volo's Guide to Cormyr = "A" ("entertain")
 * Green: Page 102, word 16, letter 3 of Volo's Guide to Monsters = "O" ("abominations")
 * Blue: Page 124, word 18, letter 2 of Volo's Guide to the Daelands = "H" ("that")
 * Purple: Page 186, word 22, letter 4 of Volos' Guide to The North = "U" ("clouds")
 * Black: Page 205, word 7, letter 6 of Volo's Guide to the Sword Coast = "F" ("unroofed")
 * White: Page 223, word 11, letter 4 of Volo's Guide to Waterdeep = "P" ("support")

"ICAO" stands for the International Civil Aviation Organization, which uses four letter codes to identify international airports (similar to the more commonly known three-letter IATA airport codes). The ICAO code "HUFP" is for Fort Portal Airport, a civilian airport in Uganda... if you want to call it an "airport". Looking at the satellite view, the airport does not have any actual buildings and it barely has a discernible runway.