A resposta pode ser encontrada na página 2 de todos os livros sob o título Na capa acompanhada da imagem completa da capa.
O PHB lê:
In this fiery scene illustrated by Tyler Jacobson, the fire giant King Snurre, suffering no fools to live, calls his hell hounds to join him in confronting unwelcome guests in his home.
O monstro na capa é um Fire Giant (MM p.154) acompanhado por Hell Hounds (MM p.182).
King Snurre é…
the final antagonist in the classic Against the Giants modules. Originally used as tournament modules, they were published in 3 parts (G1, G2 and G3) in 1978 and then together (as G1-3) in 1981. The AD&D module G1-3 is available at DMs Guild and a 5E conversion is part of Tales from the Yawning Portal. Versions were also published for other editions of AD&D and D&D.
O DMG lê:
Tyler Jacobson illustrates the arch lich Acererak as he raises an army of undead and prepares to unleash it on an unsuspecting world.
O monstro na capa é um Lich (MM p.202).
Acerak é…
the antagonist of the even-more-classic Tomb of Horrors module. Also originally a tournament, it was first published as S1 in 1978. Like G1-3, it is available at DMs Guild and part of Tales from the Yawning Portal.
Acerak has been mentioned in many, many adventures over the last 30 years. Most recently, he is (perhaps) the power behind the Tomb of Annihilation. Maybe. So much contradictory information has been written that it can't all be true. Can it?
O MM lê:
Raymond Swan land illustrates the Xanathar ambushing explorers in the darkest depths of Undermountain, proving that the beholder crime lord's interests run deep beneath the city of Waterdeep.
O monstro na capa é um Beholder (MM p.28).
Xanathar, o espectador é…
the leader of the Xanathar Thieves' Guild in Skullport, as described in many sourcebooks and modules. The 5E book Xanathar's Guide to Everything is said to be based on his research and knowledge.