As already mentioned, gigantic spiders are a common staple in fantasy games, largely due to their prominence in the writings of Tolkien.
Only about half of all spiders build webs to catch their prey, the other half actively hunt for food, like the (Giant) Wolf Spider.
Ghalans parents were set upon and killed by fierce wargs while travelling the Deepenwoods. Before the wargs were able to devour the infant they carried with the, priests of the Forest Mother came to the rescue, and chased the beasts away. The child was raised among the priests, and instructed in their ways. Now his training is complete, and he is ready to experience the world outside.
Personality traits: Deeply spiritual, Ghalan sees omens and portents in nearly everything. While some might find this somewhat frustrating at times, it means he is acutely aware of his surroundings, and able to see subtle connections, invisible to others.
Ideals: The Forest mother teaches the cycles of the seasons and life and death. Stagnation brings nothing new, and ultimately decay. Ghalan applies these same principles to everything around him, seeking to shake up and change anything that risks becoming to rigid.
Bonds: Ghalan holds the priests that rescued and raised him in very high regard. While the teachings of the Forest Mother decree that he go out and experience the world, he is feels a very strong bond to those who saved him as an infant, and would drop anything to come to their aid if needed.
Flaws: Having been brought up among pious and devout priests, Ghalan has been filled with high expectations of those around him. His disapointment is clearly visible should his companions fail to uphold the highest of standards. Still, for all his harsh judgement of others, that is nothing compared to the standards he holds for himself - he will beat himself up for event the tiniest mistake, and seek to atone for his faults, even for transgressions most people would not think twice about.
His character sheet (level 1) looks like this (created using the free "Basic Rules for Dungeons and Dragons" from Wizards of the Coast.):
Meet Golldir, dwarf axe-maid of the once proud Skörprun-clan.
Fierce and loyal, Golldir grew up the only female among nine younger brothers. Not content to be meek, or be bullied, she became every bit as tough as any of her brothers, and could match each one of them in any form of combat. Despite her superior skill and strength, Golldir still found that she was never considered the equal of her brothers among the tradition bound dwarves, and so in the end, she sought to make a name for herself adventuring.
Personality traits: No great intellectual, Golldir always prefers the simplest, most direct way of solving any problem, be that charging headlong, axe raised, into multitudes of enemies, or knocking through that door to get in. Roundabout solutions have no appeal to her, and she abhorrs subterfuge and deception.
Ideals: Though she left dwarven society because she didn't really fit in, she holds a great pride in anything dwarven, and will defend 'dwarfdom' for anyone and any thing. Those few individuals of other races she deems worthy to associate with, she thinks of as "honorary dwarves".
Bonds: She is slow to trust others, but once given she will defend her allies to the bitter end.
Flaws: Just like her bond to her allies and comrades are unflinching, so is her hatred to those she deems to be enemies - be that enemies of dwarves in general or to her and her fellow adventurers. This hatred can become so deep and unreasoning, that she might charge blindly to face them, regardless of the odds, unless someone can check her rage.
Her character sheet (level 1) looks like this (created using the free "Basic Rules for Dungeons and Dragons" from Wizards of the Coast.):
While the main difference between giant toads and giant frogs in D&D is their size, and what size adventurers they can swallow, the real difference between frogs and toads lie in their preferred habitat (toads are adapted to living in dry environments, whereas frogs need to live in or by water), the smoothness of their skin and their ability to jump (toads aren't really that great at jumping). Both frogs and toads can secrete poison, and though most toads have poison glands behind their eyes, the poison dart frog is more poisonous than any toad.
In real life, the largest toads around in the infamous cane toad the can grow up to 25 cm in length, which incidentally is smaller than the largest frog, the goliath frog, that can reach up to 32 cm in length.
In mythology, the ghoul (or ghul) actually traces its roots back to arabic folklore, where they are described as demonic spirits, related to jinns, that dwell in burial grounds or uninhabited places. Alternatively, they are described as shape shifting demons, that lure people astray in the desert. The ghoul was introduced to the western world in the eighteenth century, when Antoine Galland translated The Thousand and One Nights.
The "bug" in Bugbear probably comes from an old english word ("bugge") meaning a frightening thing, and it probably has the same roots as the word "bogeyman". I medieval litterature it was described as a creepy bear that lurked in the forests scaring children.
D&D isn't just monsters - other people inhabit the same world as the players. In RPG terms these people are known as NPC - non player characters. While some can be mighty kings, powerful knights or evil mastermind wizards, a lot of them are just plain commoners - farmers or labourers. Back in the day, these were often known as 0-level character.
In game terms normal commoners probably never pose a big threat to adventurers, except if they form large mobs....