Dragons take a long time to heal. A dragon may heal only 10 hit points per long rest while in humanoid form, and only 20 hit points per long rest in dragon form. It may be a good idea to fake your humanoid form's death if a normal player character would have died from the amount of damage taken, as this may protect your draconic identity. If your draconic form ever loses all of it's hitpoints, it may be time to start filling in a new character sheet.

You may increase three ability scores by 1 (Strength, Dexterity, Constitution, Wisdom, Intelligence, or Charisma).

For ease, only the main stages are listed.

Ages vary depending on the type of dragon. Chromatic dragons tend to live shorter lives than Metallic dragons, with Twilight happening around 2000 - 2500 years, whereas some metallic dragons can live well over 4000 years before twilight starts.

Twilight

The Twilight years are the last years of a dragon's life, where the dragon rapidly declines within a matter of a few years before death. There are only a few options that a dragon has at this stage of life:

While taking a humanoid form, you are small or medium size, depending on the race of humanoid.

Your base walking speed is 30 feet. You can also swim or climb 30 feet, and fly 80 feet. Brown dragons are able to burrow as fast as other dragons can fly. Some races of dragons, such as Mercury dragons or Yellow dragons, have a faster base walking speed. Yellow dragons are capable of moving 40ft. per 6 seconds, and Mercury dragons are capable of moving 50ft. per 6 seconds. Mercury dragons can also swim and climb 50ft. and fly 120 ft, however, using your full movement speed would likely cause other humanoids to suspect you aren't who you appear to be, so use your speed only when it is necessary. You are not able to fly in your humanoid form without revealing that you have wings.

You have draconic ancestry. Choose one type of dragon from the Draconic Ancestry table. Your breath weapon and damage resistance are determined by the dragon type, as shown in the table.

Chromatic Draconic Ancestry

*Rolling dragon ancestry is not suggested, as the breath weapon should be chosen carefully to not be overpowered. But, if you do insist on rolling for draconic ancestry, roll a d10 for the metallic dragon list, with a 10 being a Stellar, or roll a d12 for the chromatic dragon list. If you roll a 12, you are a Shadow dragon, and roll a second d12 for type. If you roll a second 12, you are a shadow metallic dragon, and roll a d10 for type. If the DM excludes Stellar or Shadow from the list, rolling either of these results in the player having choice of their ancestry.*

You can use your action to exhale destructive energy. Your draconic ancestry determines the size, shape, and damage type of the exhalation. When you use your breath weapon, each creature in the area of the exhalation must make a saving throw, the type of which is determined by your draconic ancestry. The DC for this saving throw equals 8 + your Constitution modifier + your proficiency bonus. Most saving throws require a creature to pass a Constitution or Dexterity saving throw, but Mercury dragons require a Wisdom saving throw. A creature takes 2d6 damage on a failed save, and half as much damage on a successful one. The damage increases to 3d6 at 6th level and the range of the breath attack increases by 10ft, then 4d6 at 11th level, and 5d6 at 16th level. After you use your breath weapon, you can’t use it again until you complete a short or long rest.

You have resistance to the damage type associated with your draconic ancestry.

You can speak, read, and write Common and Draconic. Draconic is thought to be one of the oldest languages and is often used in the study of magic. The language sounds harsh to most other creatures and includes numerous hard consonants and sibilants.