At 1st level gain the ability PREDATOR(not an actual ability). This ability allows you to consume a creature whose CR is 1 + your character level. After consuming your foe you gain 1 prime trait from its status charts.

this ability upgrades after absorbing 100 monsters of cr that is above that You will lose those skills for 5 days while the skill upgrades and then it will change to 2+ your level the requirements go up by 100 every time and the days you can't use your skill will also increase.

You must take a short rest once using this skill so you can absorb the skill max number of time 30 min

any creature they  absorb they will be able to become.

Upon using a hit die during a short or long rest, as long as you drink in water from any source that isn't impure you gain an extra 1d6+ con mod hp back. This effect leaves you unconscious for 1 hour until the healing is completed.YOu can heal an ally for 1d6+ con mod and then you, you can only heal one ally per short rest.

At the 18th level, you can absorb any item tool or creature that isn't considered to have legendary resistance. You can then turn yourself into this item or create a copy of it or of the creature you absorbed. This effect lasts indefinitely until you are knocked unconscious or dispelled by you. You can do this once per long rest

at the 4th level, you can use this ability to hear a voice that can be used one plus your intelligent mod, per short rest.
you can do
detect magic
identify object
analyze ( can tell you cr ratting and monster name)

neutral requirements

You must build a monster city for all creatures

-must have a rule to not attack humans

-must name all monsters.

-must have over 500 monster

-must achieve this before level 10

tell your dm about your choice and you must choose

Good choice:

The Savior Of Monster

You have convinced so many creatures to join your village by showing mercy, great skill in battle, or persuading them to join.

You gain plus 2 to your charisma and you can gain proficiency in Persuasion and deception plus expertise in them at the 10th level.

but you must create the following to gain these perks 

--must have a rule to not attack humans

--must have over 10,000 monsters (or up to the dm)

--must get a treaty signed from 3 country 

-must keep the no killing monster rule

-must gain the favor from a druid.

evil choice:

Am I Going To Become A Demon King?

If you choose this you must kill 5000 humans and you must go rest for over 5 + character level. Every day you must make a stealth check to see if you hide from the human's looking for you. while doing this you must have the following.

-A monster city (to protect you if they must)

-level 10 or above

-A reason why you must become one(not needed but it would b amazing if it used)

-someone dear to you dead(plot)

-must finish the requirements of the neutral requirements

-must have 30,000(or up to the dm)

once this is complete you gain 

 +1 to str, dex, and con + one unique skill(the dm can decide)

if you do the evil choice you don't get the perks of the savior of monster

.At 13th level you gain the ability to absorb an enemy attack, spell. (you can learn it by watching but then you will lose a reaction and can be open for an attack)

you can only have the number of your con mod + 1/2 of your character level. if you try to take any more  than that you will be damaged every hour for 5 hp

(this is for spell and enemy ability using new skill)