You Constitution score increases by 2.

Weirds being made magically, they are born knowledgeable and already mature.
As a fusion of two elementals, the aging process that Weirds go through is unstable, and their maximal age will be dictated by their inner elements.

Being a somewhat unstable fusion of two contrasting elements, Weirds are naturally chaotic, with no particular penchant towards good or evil.

Intelligent weirds are usually of same shape and size as their creators. Your size is medium.

As a being made by science, you count as both Humanoid and Construct.

With accounting your inner elements, your base movement speed is 25 feet. 

From the two element you originate from, select one that will dictate your personality and your abilities.
It must differ from the element that constitute your body.

• Fire: You're an ardent person, always warm to your friend and a raging storm against your enemies. You gain +1 to your Charisma score.
• Lightning: You cannot stay in place and is always jumping from one place to another. You gain +1 to your Dexterity score.
• Ice: You're calculated and always calm, but your cold calm stance will thaw whenever in action to let the grandiose and imposing character you've always been. You gain +1 to your Intelligence score.
• Stone: You've got a rock strong personality, always standing your ground on the opinions you believe in. You gain +1 in Wisdom.  

From the two element you originate from, one will dictate your body's ability and your outer appearance.
Your elemental body must be of a different type than your core.

• Lightning: your body is a constant and ever shifting plasma of sparkles and arcs of lightning can be often seen erupting from any of your extremities. You gain the following:
  • You move at an increased speed (+15 feet), however your body release more energy per day than other species, you need twice the food and 2 hours more of sleep per night. 
  • As an action you can also power any izzet made machinery, or electrify water you're standing on.
• Fire: your body is a constant raging and blazing storm of fire and magma, drops of liquid fires can be seen behind each of your steps. You gain the following:
  • You glowing brightly in the dark and allowing you a perfect vision in the dark.
  • As an action you can release burst of fire damaging anybody around you, and hurting yourself in the process
• Stone: you are taller than the other of your species, your stone like skin seems to be ever crumbling and reassembling, like some shifting sands compressed into rocks. You gain the following:
  • You are 10 time heavier than any other member of your kin and ignore any rough terrain.
  • You can manipulate your skin to become as tough as the most solid rocks, at the cost of your movement for this turn and the following one.
• Ice: your body is clear and crystal like, revealing your core deep within your body. You gain the following:
  • however the crystalline exterior of your body being really fragile reduce your constitution.
  • You're able to shift the consistency of your body, leaving your core exposed and dropping any object you're carrying, but allowing you to go through the smallest openings.  

Whenever you take elemental damage associated to your Energy Core or Body, you may use a reaction to try to absorb the incoming elemental damage.
To do so, you must roll a Constitution saving throw equal to the damage taken or 10, whichever is higher, on a success you gain the following:

• You gain resistance against that damage until the beginning of your next turn, this is applied before you take the triggering damage.
• You may add an additional 1d4 to your next melee or ranged attack, or use this incoming energy as your food source for that day.
  • the damage will increase to 2d4 at level 5, 3d4 at level 11 and 4d4 at level 17.

At higher level, you body can intake higher source of energy, the DC to beat wiil be: 

• Constitution Save of 10 or half of the damage taken at level 5
• Constitution Save of 10 or a third of the damage taken at level 11
• Constitution Save of 10 or a quarter of the damage taken at level 17