There was one class in the prestige class appendices, I think it was called monarch’s chosen, that allowed you to become something of a smaller dragon but also wholly bound to your SK.
For fun, I made an advanced being bloodline sorcerer subclass for 5e that allowed you to awaken the power in your blood and eventually be able to transform temporarily into a miniature version of your ancestor. It’s very unrefined but maybe it will give you some ideas.
Advanced Being Bloodline
At 1st level, choose one of the following types of advanced being as your ancestor: avangion, dragon, elemental lord* or spirit of the land. Your chosen ancestor determines some of the features you gain later.
*If you chose elemental lord, you must also choose the specific element and energy associated with its type- air (thunder), earth (acid), fire (fire), magma (fire), rain (lightning), silt (necrotic), sun (radiant) or water (cold).
Starting at 1st level, you learn additional spells when you reach certain levels in this class, as shown on the psionic arcana table. The table shows the general spells that are added to the sorcerer spell list for you, along with the spells associated in the table with your ancestor’s advanced being type.
Each of these spells counts as a sorcerer spell for you, but it doesn’t count against the number of sorcerer spells you know.
you can cast one 1st-level spell of the general or your chosen ancestor column in the psionic arcana table once without expending a spell slot. Once you cast a spell in this way, you can’t do so again until you finish a long rest.
|Spirit of the land Spells
|Elemental lord Spells
|Mind sliver, command
|Pass without a trace
|Protection from energy
|Aura of vitality
|Aura of life
|Commune with nature
|Summon draconic spirit
Being descended from an immortal being of unimaginable power, you inherited something of their deathless nature. At 1st level, your supernatural parentage manifest itself in your physiology, bestowing you with the following benefits:
- You have advantage on saving throws against disease and being poisoned, and you have resistance to poison damage.
- You have advantage on death saving throws.
- You don’t need to sleep, and magic can’t put you to sleep. You can finish a long rest in 4 hours if you spend those hours in an inactive, motionless state, during which you retain consciousness.
- you age more slowly. For every 10 years that pass, your body ages only 1 year.
Self Defiling (optional rule): advanced being bloodline sorcerers who chose avangion, spirit of the land or elemental lord of air, earth, fire, water or rain as their ancestor cannot defile the land. Instead they can draw on their own powerful lifeforce to bolster their spells. Whenever you apply metamagic to your spell, you can reduce its sorcery point cost by a number equal to half your proficiency bonus (rounded down, minimum of 1). Alternatively, they can Double their proficiency bonus added to the spell save DC.
Beginning at 6th level, you gain a shadow of your ancestor’s ability to merge magic and psionics. When you cast any spell of 1st level or higher from your psionic arcana list, you can cast it by expending a spell slot as normal or by spending a number of sorcery points equal to the spell’s level. If you cast the spell using sorcery points, it requires no verbal or somatic components, and it requires no material components, unless they are consumed by the spell.
At 6th level, your powerful ancestry manifest itself further, giving you one of the following abilities that is associated to your chosen ancestor:
*Avangion- you gain the ability to channel the powerful energies inherent in your lifeblood to heal yourself and others. As an action, you can touch a creature and heal a number of hit points equal to double your charisma modifier. You can do so a number of times equal to your proficiency bonus, and you regain all uses of this ability after completing a long rest. This ability doesn’t affect constructs and undead.
*Dragon- you inherited a measure of your ancestor’ ability to defile animal life. By swallowing a small obsidian orb to focus your power you can now use it to your advantage. You gain the ability to target one living creature you can see within 30ft of you, and that creature becomes incapacitated until the start of its next turn. You then gain a number of sorcery points equal to half your proficiency bonus (rounded down, minimum of 1). Once you use this ability you can’t use it again until you finish a long rest. This ability doesn’t affect constructs and undead.
*elemental lord- you gain resistance to the energy type associated with your ancestors element. Additionally, when you cast a spell using a spell slot that deals that damage type, you emit an aura of elemental power, which extends 5 feet from you in every direction (but not through total cover) and lasts until the end of your next turn. While the aura is active, each creature of your choice has resistance to your chosen damage type while within the aura, as you infuse them with your elemental essence.
*spirit of the land- your natural connection to the land allows it to share some of its power with you. Once per long rest, you can cast one spell of the druid spell list without expanding a spell slot. The spell must be of a level you already have access to.
Starting at 14th level, you can use a bonus action to focus your inherited power to fly. While this power is active, you have a flying speed of 30 feet and can hover. This power lasts until you’re incapacitated, you die, or you dismiss it as a bonus action.
Your ancestry determines the way you manifest this ability: gossamer wings that shine with an otherworldly light for an avangion, leathery bat-like wings for a dragon, a vortex of elemental energy for an elemental lord and shimmering aura of golden-green life energy for spirit of the land.
Upon reaching 18th level, you can use an action to forcibly awaken your ancestor’s latent blood within you. You assume a form reminiscent of your ancestor’s, granting you the following benefits and drawbacks:
- You gain a +4 bonus to AC, as your flesh becomes either radiant silver (avangion), covered by iron hard scales (dragon), shifts back and forth into elemental matter (elemental lord) or assumes aspects of the surrounding environment (spirit of the land).
- You have advantage on attack rolls and saving throws.
- When you hit a target with a weapon attack or spell attack, that target takes an extra 1d10 force damage.
- Any weapon attack against you scores a critical hit on a roll of 18–20, since underneath your augmented defenses your quasi-transformed anatomy is left more vulnerable to damage.
When this effect ends,you immediately drop to 0 hit points and are dying. Once you use this feature, you can’t use it again until you finish a long rest.