Icons adapted from the Noun Project:
Nation icon/Undead promotion: Skull by Vladimir Belochkin
Arms Merchant: dollar target by Rockicon
Infection: Biohazard by LUTFI GANI AL ACHMAD
National Tombstone/Hard to Kill Twice: Grave by Kmg Design
Germ Warfare/Sickening Plague: virus by Nawicon
Black Death: Death by tulpahn
Ghost: Ghost by Dmitry Baranovskiy
Lich King/Summon the Lich King: Crown by Vladimir Belochkin and Skull by Vivian Ziereisen
Lich King's Tomb: Ankara by ProSymbols
Graveyard: graveyard by Nikita Kozin
Memento Mori: Tombstone by Sneha
Abyss: canyon by iconfield
Bone Dragon: dragon by BGBOXXX Design
Necromancer: necromancy by HeadsOfBirds
Mass Grave: Mass Grave by Dan Hetteix
Tasty Brains: Brain by AFY Studio
Breach the Walls: disruptor by Luis Prado
Eat the Living: fork and knife by John Winowiecki
Angel of Death: wings by Luis Prado
Morgue: morgue by MonoGraphic, ES
Gravedigger: Shovel by Milinda Courey
Pixel art:
Graveyard and Abyss tile improvements by ekids789789#4813 on Discord
Arms Merchant, Black Death, Bone Dragon, Ghost, Warrior-Undead and Lich King units by GeneralWadaling#2878 on Discord
All other pixel art based on units by GeneralWadaling#2878 with minor modifications by Lodo the Bear