Chris Pine agreed to appear because the role of Edgin is very atypical for a fantasy-film leading man and because he sat in on his nephew playing a D&D campaign and saw how much fun he and his friends were having.
The characters from the television cartoon Dungeons & Dragons (1983) make an appearance during the High Sun Games. When Holga spots another team excited that they found a chest, she stops to watch. Hank the Ranger opens the chest and Bobby the Barbarian takes the axe. Sheila the Thief and Diana the Acrobat are standing beside them. When the group leaves, you can just make out Eric the Cavalier's head behind Presto the Magician's signature hat. This same group is in the "safe cage" at the end of the round, where you get a good look at Eric the Cavalier.
The directors opened up about Monty Python's influence on the film, with Jonathan Goldstein explaining that while the creative team wanted to make a comedy, they didn't want to mock the source material. "We never want to go too far where it becomes a spoof of fantasy films, but we also wanted to be able to pivot from something creepy and traditional fantasy to an absurd, almost Monty Python-type sequence," the director said.
All the spells used in the film, while largely unnamed, are all spells used in the Dungeons & Dragons tabletop RPG.
Wizards of the Coast (which owns Dungeons and Dragons) made stat blocks for the main characters showing their abilities and attributes.