Maybe it has a lower Int, and a Higher Wis
d10-- beasts,magical beasts, constructs, oozes all have a HD D10
D12--Dragons, Undead all have a HD d12
So by process of sorting
the Rangoon wont be a construct an ooze.
Magical beasts Magical beasts have dark vision with a range of 60 ft, and low light vision.
A Colossal Magical beast would have a HD of 32d10 have a Slam damage of 2d6, a Bite of 4d6, a Claw of 2d8, and a gore of 4d6
Advantages Decent intelligence, and wisdom, still an animal of a sorts, gets supernatural or extrodinary abilities, and has a BAB as fighter
New ideas on dragons
how about a dragon without wings something more like the chinese dragon, or the Serpent dog from Never ending story
There is a neat idea remember the white canine looking serpent in Neverending Story Had no wings and could fly well howsabout
Can not fly is a green brown colored serpent dog with large trunk like legs. He isnt very smart but he is wise, always filled with sage advice for the people that worship him.
He has the Sonic breath weapon Sentinals song ( A singing sound that raises in pitch until it begins to deafen and destroy things)
And he is a small god (out of the article in dragon # 293 worshiped by the peasant folk, and nobles alike in the small backwater country in which he lairs.
Travellers who journey through and need healing can receive such at a little wayward shrine at the edge of the forest, which is maintained by whoever uses the shrines service, and only those who share a bit of their food will receive healing from the Rongoon's shrine. ( I would make him a d8 Aberation much like the naga and add the half dragon template, or the half celestial)
When the paladin comes to kill this creature he finds it a peaceful and helpful being ( maybe after he kills it) who is the guardian of his wooded homeland. Rumours have placed the Rongoon in more than one place at one time and many feel that this proves the beings godhood. However this is not so. There are two of these beings in the land One Rongoon-Sar, watches over the children that play in the woods, leaves food out for the elves, and will heal folk who stop by his shrine. Rongoon-dor on the other hand is evil born of a hatred for all mankind he has been terrorizing the realms that pay not his tribute more intellegent than his brother, Dor has worked a deal out with the High priestess of Rongoon in which he will force outlying nations to believe in the might of his [brothers] Church. Because of this fear of him and the faith that Rongoon-Sar has been given both Rongoon's are capable of granting spells up to 4th level And both of the Rongoon's have the Domain Nature, Rongoon-Sar is capable the Domain plant, and Rongoon-Dor is capable of the domain Treachery.