I figured this would be a helpful resource for those wondering who has been featured in SHIELD Training**.**
#1) 09/28/2017:
Featured: Rogue (Classic)
Classic Essentials: Cyclops (Classic), Professor X (Charles Xavier), Wolverine (X-Force)
*** From this point on, SHIELD Training began requiring the most recently released 4-star character as the Latest Essential, along with two older Classic characters. ***
#2) 10/19/2017:
Featured: Nightcrawler (Classic)
Latest Essential: Rogue (Classic)
Classic Essentials: Elektra (Unkillable), Invisible Woman (Classic)
#3) 11/15/2017:
Featured: The Hulk (The Main Event)
Latest Essential: Nightcrawler (Classic)
Classic Essentials: Star-Lord (Legendary Outlaw), Thor (Goddess of Thunder)
#4) 11/30/2017:
Featured: Nico Minoru (Runaways)
Latest Essential: The Hulk (The Main Event)
Classic Essentials: Iron Man (Hulkbuster), Nick Fury (Director of S.H.I.E.L.D.)
#5) 12/24/2017:
Featured: America Chavez (Young Avengers)
Latest Essential: Nico Minoru (Runaways)
Classic Essentials: Carnage (Cletus Kasady), Kingpin (Wilson Fisk)
#6) 01/11/2018:
Featured: Kraven the Hunter (Sergei Kravinoff)
Latest Essential: America Chavez (Young Avengers)
Classic Essentials: Ant-Man (Scott Lang), The Thing (Classic)
#7) 02/08/2018:
Featured: Black Panther (King of Wakanda)
Latest Essential: Kraven the Hunter (Sergei Kravinoff)
Classic Essentials: Deadpool (X-Force), Sam Wilson (Captain America)
#8) 02/22/2018:
Featured: Shuri (Master Engineer)
Latest Essential: N/A
Classic Essentials: Ghost Rider (Johnny Blaze), Jean Grey (All-New X-Men), Mr. Fantastic (Reed Richards)
*** Note for #8 they chose to deviate from their usual pattern and feature three Classic characters. This was because the would-be Latest Essential (Black Panther) was not yet in tokens. ***
*** From this point on the Latest Essential switched from being the newest 4-star released to the one set to leave the Latest Legends pool. ***
#9) 03/22/2018:
Featured: Valkyrie (Asgardian Warrior)
Latest Essential: Vulture (Adrian Toomes)
Classic Essentials: Red Hulk (Thunderbolt Ross), X-23 (All New Wolverine)
#10) 04/05/2018:
Featured: Jubilee (Uncanny X-Men)
Latest Essential: Mockingbird (Bobbi Morse)
Classic Essentials: Iceman (All New X-Men), The Hulk (Totally Awesome)
#11) 05/03/2018:
Featured: Black Widow (Infinity War)
Latest Essential: Yondu (Awesome Mix Volume 2)
Classic Essentials: Spider-Woman (Jessica Drew), Venom (Eddie Brock)
#12) 05/31/2018:
Featured: Spider-Man (Infinity War)
Latest Essential: Lockjaw (Royal Bulldog)
Classic Essentials: Drax (The Destroyer), Nova (Sam Alexander)
*** On 06/06/2018 dilution returned and so there is technically no distinction between Classics and Latests. ***
#13) 06/13/2018:
Featured: Wiccan (Billy Kaplan)
Newer Essential: Rogue (Classic)
Older Essentials: Spider-Man (Miles Morales), Quake (Daisy Johnson)
#14) 07/12/2018:
Featured: Ghost (Quantum Thief)
Newer Essential: Nightcrawler (Classic)
Older Essentials: Spider-Gwen (Gwen Stacy), The Punisher (MAX)
#15) 07/26/2018:
Featured: Emma Frost (Astonishing X-Men)
Newer Essential: Spider-Man (Infinity War)
Older Essentials: Ant-Man (Scott Lang), X-23 (All New Wolverine)
*** Note for #15 they chose to deviate from their usual pattern and made two older character who have already been required (Ant-Man and X-23) essential again in lieu of those who haven’t had a chance to be essential. ***
#16) 08/23/2018:
Featured: Nebula (Infinity War)
Newer Essential: Shuri (Master Engineer)
Older Essentials: War Machine (James Rhodes), Winter Soldier (Bucky Barnes)
#17) 09/06/2018:
Featured: Dazzler (Classic)
Newer Essential: N/A
Older Essentials: Iron Man (Hulkbuster), Kate Bishop (Hawkeye), Moon Knight (Marc Spector)
*** Note for #17 they chose to deviate from their usual pattern and required three older characters, including one who was already essential (Iron Man). ***
#18) 10/04/2018
Featured: Taskmaster (Tony Masters)
Newer Essential: Emma Frost (Astonishing X-Men)
Older Essentials: Peggy Carter (Captain America), Wasp (Janet Van Dyne)
#19) 11/01/2018
Featured: Domino (X-Force)
Newer Essential: Dazzler (Classic)
Older Essentials: Gwenpool (Gwen Poole), Luke Cage (Power Man)
#20) 11/15/2018
Featured: Bishop (Classic)
Newer Essential: Emma Frost (Astonishing X-Men)
Older Essentials: Blade (Modern), Venom (Agent Venom)
#21) 11/29/2018
Featured: Prowler (Aaron Davis)
Newer Essential: Dazzler (Classic)
Older Essentials: Captain Marvel (Carol Danvers), Medusa (Inhuman Queen)
#22) 12/24/2018
Featured: Spider-Ham (Peter Porker)
Newer Essential: N/A
Older Essentials: Agent Coulson (Agents of SHIELD), Ghost Rider (Johnny Blaze), Riri Williams (Ironheart)
*** Note for #22 they chose to deviate from their usual pattern and required three older characters, including one who was already essential (Ghost Rider). ***
#23) 01/31/2019
Featured: Namor (The Sub-Mariner)
Newer Essential: Domino (X-Force)
Older Essentials: Cloak & Dagger (Classic), Mordo (Master of the Mystic Arts)
#24) 02/14/2019
Featured: Magik (Classic)
Newer Essential: Bishop (Classic)
Older Essentials: Iron Fist (Danny Rand), Rocket & Groot (Awesome Mix Volume 2)
#25) 03/14/2019
Featured: Talos (Skrull Warlord)
Newer Essential: Namor (The Sub-Mariner)
Older Essentials: Cyclops (Classic), Gamora (Awesome Mix Volume 2)
#26) 04/18/2019
Featured: Thanos (Endgame)
Newer Essential: N/A
Older Essentials: Carnage (Cletus Kasady), Moon Knight (Marc Spector), Nick Fury (Director of S.H.I.E.L.D.)
*** Note for #26 they chose to deviate from their usual pattern and required three older characters, all of whom were already essential ***
#27) 05/02/2019
Featured: Hawkeye (Ronin)
Newer Essential: Magik (Classic)
Older Essentials: Professor X (Charles Xavier), Sandman (Flint Marko)
#28) 05/23/2019
Featured: Sabretooth (Victor Creed)
Newer Essential: Thanos (Endgame)
Older Essentials: Thor (Goddess of Thunder), Wolverine (X-Force)
#29) 06/20/2019
Featured: Black Cat (Master Thief)
Newer Essential: Hawkeye (Ronin)
Older Essentials: Kingpin (Wilson Fisk), Star-Lord (Legendary Outlaw)
#30) 07/04/2019
Featured: Mysterio (Quentin Beck)
Newer Essential: N/A
Older Essentials: Peggy Carter (Captain America), Invisible Woman (Classic), Elektra (Unkillable)
#31) 08/01/2019
Featured: Juggernaut (Fear Itself)
Newer Essential: Sabretooth (Victor Creed)
Older Essentials: The Hulk (The Main Event), America Chavez (Young Avengers)
#32) 08/29/2019
Featured: Human Torch (Jim Hammond)
Newer Essential: Mysterio (Quentin Beck)
Older Essentials: Black Panther (King of Wakanda), The Thing (Classic)
#33) 09/19/2019
Featured: Captain America (Worthy)
Newer Essential: Juggernaut (Fear Itself)
Older Essentials: Hawkeye (Ronin), Mockingbird (Bobbi Morse)
#34) 10/10/2019
Featured: Spider-Man 2099 (Miguel O’Hara)
Newer Essential: Human Torch (Jim Hammond)
Older Essentials: Spider-Gwen (Gwen Stacy), Spider-Man (Infinity War)
Below is every 4* listed in release order. Next to them (if applicable) is a number representing which SHIELD Training they were featured in. As you can see, while jumping around a bit, they are definitely targeting the oldest characters first. Should give a rough idea what to expect moving forward.
Wolverine (X-Force) #1, #28
Invisible Woman (Classic) #2, #30
Nick Fury (Director of S.H.I.E.L.D.) #4, #26
Devil Dinosaur (Gigantic Reptile)
Thor (Goddess of Thunder) #3, #28
Elektra (Unkillable) #2, #30
Star-Lord (Legendary Outlaw) #3, #29
Professor X (Charles Xavier) #1, #27
Kingpin (Wilson Fisk) #5, #29
Iron Man (Hulkbuster) #4, #17
Carnage (Cletus Kasady) #5, #26
The Thing (Classic) #6, #32
Ant-Man (Scott Lang) #6, #15
Jean Grey (All-New X-Men) #8
Deadpool (X-Force) #7
Sam Wilson (Captain America) #7
Mr. Fantastic (Reed Richards) #8
Iceman (All New X-Men) #10
Cyclops (Classic) #1, #25
Red Hulk (Thunderbolt Ross) #9
X-23 (All New Wolverine) #9, #15
Ghost Rider (Johnny Blaze) #8, #22
The Hulk (Totally Awesome) #10
Miles Morales (Spider-Man) #13
Venom (Eddie Brock) #11
Nova (Sam Alexander) #12
Spider-Gwen (Gwen Stacy) #14, #34
Quake (Daisy Johnson) #13
The Punisher (MAX) #14
Howard the Duck (Howard, a Duck)
Drax (The Destroyer) #12
Winter Soldier (Bucky Barnes) #16
War Machine (James Rhodes) #16
Kate Bishop (Hawkeye) #17
Moon Knight (Marc Spector) #17, #26
Peggy Carter (Captain America) #18, #30
Wasp (Janet Van Dyne) #18
Spider-Woman (Jessica Drew) #11
Luke Cage (Power Man) #19
Gwenpool (Gwen Poole) #19
Blade (Modern) #20
Venom (Agent Venom) #20
Medusa (Inhuman Queen) #21
Captain Marvel (Carol Danvers) #21
Riri Williams (Ironheart) #22
Mordo (Master of The Mystic Arts) #23
Agent Coulson (Agents of SHIELD) #22
Iron Fist (Danny Rand) #24
Cloak & Dagger (Classic) #23
Rocket & Groot (Awesome Mix Volume 2) #24
Gamora (Awesome Mix Volume 2) #25
Sandman (Flint Marko) #27
Vulture (Adrian Toomes) #9
Mockingbird (Bobbi Morse) #10, #33
Yondu (Awesome Mix Volume 2) #11
Lockjaw (Royal Bulldog) #12
The following characters had covers rewarded in SHIELD Training
Rogue (Classic) #2, #13
Nightcrawler (Classic) #3, #14
The Hulk (The Main Event) #4, #31
Nico Minoru (Runaways) #5
America Chavez (Young Avengers) #6, #31
Kraven the Hunter (Sergei Kravinoff) #7
Black Panther (King of Wakanda) #32
Shuri (Master Engineer) #16
Valkyrie (Asgardian Warrior)
Jubilee (Uncanny X-Men)
Black Widow (Infinity War)
Spider-Man (Infinity War) #15, #34
Wiccan (Billy Kaplan)
Ghost (Quantum Thief)
Emma Frost (Astonishing X-Men) #18, #20
Nebula (Infinity War)
Dazzler (Classic) #19, #21
Taskmaster (Tony Masters)
Domino (X-Force) #23
Bishop (Classic) #24
Prowler (Aaron Davis)
Spider-Ham (Peter Porker)
Namor (The Sub-Mariner) #25
Magik (Classic) #27
Talos (Skrull Warlord)
Thanos (Endgame) #28
Hawkeye (Ronin) #29, #33
Sabretooth (Victor Creed) #31
Black Cat (Master Thief)
Mysterio (Quentin Beck) #32
Juggernaut (Fear Itself) #33
Human Torch (Jim Hammond) #34
Captain America (Worthy)
Spider-Man 2099 (Miguel O’Hara)