You count as one size larger when determining your carrying capacity and the weight you can push, drag, or lift. (this ability is still active during Monstrous Transformation)

Your Strength score increases by 1, and your Constitution score increases by 2.

Young Kaijyn grow more slowly than the average humanoid. They usually crawl after hatching or being birthed, attaining the size and development of a 10-year-old human child by the age of 20, and reach adulthood by 40-50. They live to be around 80-300 depending on whether they suffered any birth defects or if their genes are stable.

Kaijyn are renowned for their size, but in their more humanoid form aren't that different from the average humanoid height speaking. taller and heavier than humans, standing around 5-7 feet tall and averaging almost 250-400 pounds in their base form. Their size is medium.

Your base walking speed is 30 feet.

You have monstrous ancestry. Choose one damage type from the Monstrous Birthparents table. Your elemental Birth Mutation damage and damage resistance are determined by the monster type, as shown in the table.

Monstrous Birthparents

As your body begins to develop and evolve unlocking its full potential, you can choose a mutation at lvl 1, 3 & 5 that will manifest in your Monstrous Transformation.

At 1st level, choose one of the following options:

• Elemental Blood. Whenever a creature makes a successful melee attack against you, they need to make a DC10+ your Con modifier Con save or take 1d6 + your Con modifier in your chosen Elemental Damage Type.
• Mountain Conquerer. You have a climbing speed equal to your walking speed.
• Leviathan. You can breathe air and water, and you have a swimming speed equal to your walking speed.
• Breathe Weapon. Deal 2d6 of your chosen Elemental Damage Type in a 20ft cone or 40ft line, and half as much damage if the targets pass a saving throw of DC10 + your Con Modifier +Proficiency against your elemental damage type. The damage increases to 3d6 at 3rd level, 4d6 at 6th level, 5d6 at 9th level, 6d6 at 12th level, 7d6 at 15th level, and 8d6 at 19th level

• Titan's Crest. You have a large set of horns or a dense crest as a Natural Weapon. You are proficient with your horns, which are a melee weapon that deals 2d6 + Dex Modifier piercing or bludgeoning damage. Your horns grant you advantage on all checks made to shove a creature, but not to avoid being shoved yourself.When you use the Dash action during your turn, you can make a melee attack with your horns as a bonus action. Alongside to dealing an additional 1d6 piercing/bludgeoning damage with a dash, you can choose to shove a number of opponents OR knock a number of creatures prone if you pass through their space with the Dash action.

At 3rd level, your monstrous form unlocks its further potential, developing new characteristics. Choose one of the options you didn't take at 1st level, or one of the following options:

• Additional Limbs. You have one or two special additional appendages growing alongside your arms, legs, heads, tail or other bodily protrusions. Choose whether they're claws, hands, tentacles, etc. You gain an additional bonus action where you can only use the singular/pair of limbs to perform an attack, you can use one of them to try to grapple a creature. Each one is also a natural weapon, which you can use to make an unarmed strike. If you hit with it, the target takes bludgeoning, piercing, or slashing damage equal to 2d6 +your Strength modifier. Immediately after hitting, you can try to grapple the target as a bonus action. These appendages can't precisely manipulate anything and can't wield weapons, magic items, or other specialized equipment unless the DM approves of doing so. This Birth Mutation can be taken again at 5th level.
• Armored Plating. Your skin in places is covered by a thick keratin shell. You gain a +2 bonus to AC when you're not wearing heavy armor, as an action you can enter a hibernation mode where you fold up into an armoured ball like an armadillo and gain an additional +2 AC for one round, but can't do anything else for the entire round.
• Elemental Burst. You have an organ that produces a 1d10 burst of your chosen Elemental Damage in a 60ft sphere, succeeding a DC equal to 8 +your Constitution modifier +Proficiency. This damage increases by 1d10 when you reach 9th level (2d10), again at 12th level (3d10) and 17th level (4d10).
• Flying Appendages. You gain a 60ft flying speed
• Excavator. You gain a 60ft burrowing speed

At 5th level, your monstrous form finishes developing. Choose one more option you didn't take at 1st level, 3rd, or one of the following options:

• Camouflage. You cloak into the environment becoming nearly invisible, while activated creatures have disadvantage on perception checks and ranged attacks against you.
• Grappling Membrane. You gain a frog-like tongue, tentacles, or other bodily protrusion you can use to perform the grapple action on a creature within a 50ft sphere, while grappled, you can move them around within the 50ft sphere until they break free.
• Pheromone Glands. You emit an ora of pheromones that surround you in a 20ft sphere, any creature that enters this area must make a DC10 + your Constitution modifier Con saving throw or risk being charmed for 1d4 rounds, the ability can only be used once per transformation, and only lasts 5 rounds.
• Paralysing Telson. Attached to your tail or any other limb is a Stinger as a natural weapon, dealing 1d8 + your Con Modifier in Piercing Damage. After being hit by the Telson the creature must make a DC10 + your Constitution modifier Con saving throw or risk being paralysed for 1d4 rounds.
• Fallout. When in your Monstrous Form you passively create patches of your elemental damage where ever your walk/swim, these patches deal 1d4 of your given elemental damage whenever someone is standing on it and disappears after 3 rounds.
• Mountainous Refinement. When in your Monstrous Form, every time you successfully hit someone with any of your abilities, attacks, actions, etc. you produce 1d4GP worth of unrefined ore on a rocky protrusion on your back, which if removed before your revert back to your Humanoid Form, it can be sold, refined, and used for crafting. You can select which of the given ores you produce from the table bellow. 
  

  Metal	Cost per lb.	Ferrus?	AC	Description
  Adamantine	5,000 gp	ferrous	23	An alloy of adamant (a strong but brittle metal), silver and electrum. Adamantine  is black,  but  has  a  clear  green  sheen  in  candlelight – a  sheen  that sharpens  to  purple-white  under  the  light  given  off  by  most  magical  radiances  and  by  will-o-wisps.
  Brass	3 sp	Non-ferrous	16	A yellow-ish metal that somewhat resembles gold. An alloy of copper and zinc.
  Bronze	4 sp	Non-ferrous	18	A red-ish brown metal. An alloy of copper and tin
  Cold Iron	4 sp	ferrous	20	Cold iron is iron found in a pure state (either meteoric iron or an especially rich ore) and is forged at a lower temperature to preserve its delicate properties.
  Copper	5 sp	Non-ferrous	16	This well-known pure metal has a distinctive pinkish sheen.
  Electrum	25 gp	Non-ferrous	20	A natural alloy of silver and gold.
  Gold	50 gp	Non-ferrous	15	This well-known pure metal is the softest of workable metallic substances.
  Iron	1 sp	ferrous	19	Iron is a silver-white malleable metal that readily rusts in moist air, occurs native in meteorites and combined in most igneous rocks. It is the most used of metals.
  Lead	2 sp	Non-ferrous	14	Lead is a heavy, grey, soft, malleable, metal.
  Mithral	2,500 gp	Non-ferrous	21	This silvery-blue, shining metal is derived from soft, glittering, silvery-black ore.
  Platinum	500 gp	Non-ferrous	20	This light gray metal with very slight bluish tinge is strong, difficult to melt, and resistant to most chemicals.
  Silver	5 gp	Non-ferrous	17	This relatively common valuable metal is the most associated with and suitable for magic.
  Steel	4 gp	ferrous	19	Steel is an alloy made out of Iron and Carbon.
  Tin	3 sp	Non-ferrous	12	A soft, silvery-white metal that is often combined with other metals or used as a layer to protect various metals.

As a bonus action, you can assume a your monstrous form. This transformation lasts for 2 minute, until you die, or until you revert to your normal appearance as a bonus action. When you are in your monstrous state you gain the following temporary benefits...

• Gain hit points equal to five times your level,
• You becomes 10 + your Con Modifier ft tall and your size becomes Large.
• Your Strength and Wisdom increases by 2
• Your base unarmed attack dice becomes 2d4 and you gain the following actions...
    – Bite: 2d10 + Strength mod Piercing
    – Tail: 2d10 + Dexterity mod Bludgeoning
• your movement speed increases by 10ft
• Your Self attack range doubles from 5ft to 10ft
• You deal double damage to structures
• You count as a mount

You also get the following temporary downsides...
• Your equipment doesn't grow with you, this includes Armor, Weapons, and Magic Items unless you cast Enlarge/Reduce Size on them, or they are tailor made for your current size. (ask a DM's permission if you wish to override this rule.)
• You lose the ability to speak any language besides Sylvan or Draconic if known (You can perform the vocal components of spells if your DM allows it)
• You cannot use the Druid's Wildshape, and any variation or Polymorph or Shapechange.

In this form you are still able to perform spells and use any class abilities not explicitly mentioned as being prohibited (e.g. Rage, Lycanform, Enlarge/Reduce Size on self, Smite, etc.).
Once you transform, you can’t do so again until you finish a short or long rest.

You can speak, read, and write Common and Draconic or Abyssal. Both Draconic and Abyssal are thought to be the oldest languages and are often used in the study of magic and monsters. Both languages sounds harsh to most other creatures and includes numerous hard consonants and sibilants.