More D&D monster facts:

• The age-old animosity between dwarves and ogres stems from a secret that ogres keep – namely, that dwarves are delicious. Ensuring that this secret does not spread is dwarfkind’s first priority, and the stereotype of ogres as compulsive cannibals has been cultivated primarily to ensure that nobody believes them when they try to explain.
  
  
• The popular belief that kobolds are descended from dragons, though false, is not entirely without merit: in fact, dragons are descended from kobolds. The particulars of how this came about are poorly understood, as kobolds are disinclined to write things down, but alcohol is believed to have been a factor.
  
  
• The creatures we think of as trolls are actually biological vehicles piloted by a race of very small, very quick humanoids. Trollish “regeneration” is nothing more than these creatures rushing about making speedy repairs; acid halts the process because occupational safety regulations prohibit the repair crews from working in the presence of chemical spills.
  
  
• The reason all goblins look so similar is that there’s just the one goblin. In the face of mortal peril, it reflexively teleports as far from the threat as possible, in both space and time; thus entire civilisations have formed from the impossibly tangled timeline of a single immortal being. As a creature of a very short memory, it has no idea that this is the case.
  
  
• There is no such thing as the tarrasque; the creature is a plausibly deniable fabrication employed to explain away the collateral damage of poor decisions by high-level adventuring parties.