Mythical beasts that need more attention

[Whizbang Dustyboots]

Which "treatment" did Rakshasas receive?

Additional types and they're made one of the big bads of the setting in a very credible way. Rakshasas are scary in Eberron.

 

[Blackrat]

Trolls. As in northern european trolls. Nasty buggers that come in various sizes (from small to at least gargantuan, possibly even colossal) and are more closely related to fey than giant and turn to stone in sunlight. I'm actually in the middle of creating it as a d&d monster. Probably make it monstrous humanoid allthough fey would still fit better to fluff.

 

[Tonguez]

There's surely some stuff worth using out there, but I think most of what you'd end up with is OCD vampires that are compelled to count mustard seeds whenever they see them. Folklore generally doesn't try too hard to make sense.

But see I like that. I'd put it in an Optional quirks box at the end of the Monster Desrciption with the instruction that "Creatures of this type do vary and may display one or more optional Quirks including:
1. are compelled to count mustard seeds whenever they see them
2. will cower if they hear religious hymns
3. may not cross a threshhold unless invited by the owner of the building
4. Etc"
DMs are encouraged to create there own quirks

I'd also include in the rules that Bardic Knowledge and appropriate Knowledge skills allow a character to learn about the specific quirks of a creature

 

[Jesus_marley]

Doug McCrae, Jesus_marley, rycanada, Voadam:

I know that it's easy to come up with a bigger badder version of these monsters to make them more memorable, but what I'd like is a monster with a built-in "Holy crap it's the Terrasque!".

Because it's been written as a singular creature, the Terrasque has a mythic appeal to it that the others don't; the players instinctively know there's only one. But I've never read birthright, and I suppose they do what they can to create that sort of feel. I'll check it out.

I wasn't merely talking about advancing a creatures stats, but also creating a history for the critter. A creature of legend doesn't get that way in a vaccuum (unless of course is from space....). It requires sightings, encounters with mundane folk who miraculously survived and spread the tale around. You as the GM provide the Holy Crapness to the creature in how you present it. In describing it, you can make mention that the creature is a manticore, or Chimera, or whatever but unlike any thats ever been seen.

 

[Drowbane]

Creature of Legend, the Epic Level Handbook's Paragon template, advancing hit dice, it's doable.

Don't forget the Kaiju template!