Your strength score increases by 7 and your constitution score increases by 6

You are immune to fire and poison damage 

without wearing armour your Ac is 22+ your  dexterity modifier

your hit point maximum increases by 15 and increases by 15 with every level

your weapon damage die is quadrupled

Your melee reach  increases  to 20 feet

Your unarmed strikes deal 4d10+str damage on a hit

You are a construct not humanoid

you don’t require food , water ,or sleep and don’t need to  breathe.

You can speak read and write common 

You can cast finger of death (9th level version) at will  it’s range is 120 feet

Your base walking speed is 45 feet 

you can’t swim in water and sink in it .when sunken you can walk on the bottom use your walking speed but it drops to 30 feet in water 

Extreme iron golems stand between 45 and 80 feet tall. your size is gargantuan

You can ignore class,level,cost and time requirements for a manual of iron golems. You can use the manual as a bonus action to instantly make the golem