True Dragon

The term "true dragon" refers to dragons that become more powerful as they age.

Dragon aging

True dragons go through twelve stages of growth during their possibly infinite lifespan. While size is dependent on the subspecies of a dragon, the great wyrms are known to be more than 30 meters in length. Unlike most humanoid species age does not seem to diminish their strength, intelligence, or power, but rather the opposite. The oldest of the wyrms are also the most formidable and impressive.

Stage	Category	Years
1	Wyrmling / Hatchling	0-5
2	Very Young	6-15
3	Young	16-25
4	Juvenile	26-50
5	Young Adult	51-100
6	Adult	101-200
7	Mature Adult	201-400
8	Old	401-600
9	Very Old	601-800
10	Ancient / Venerable	801-1 000
11	Wyrm	1 001-1 200
12	Great Wyrm	1 201+

Duling dragons by Wizards of the Coast