[Item Concepts] Evolution Stone, Evolving Armour and Evolving Wepon
Note: numbers can be tweaked
Evolution Stone: 
+ 1600 gold (total 2000 gold)
Stats: 150hp (yes that's right, no stat change from the ruby xtal)
Unique Passive - We're out of Stock: Cannot be bought after 15 minutes
Unique Passive - Only 1 in store: Can only buy 1 evolution stone the whole game
Evolving Armour: Evolution Stone + + 300 gold (Total cost 2700)
Base Stats: 300HP
Unique Passive: Adaptable Armour. After 30 minutes, distrubutes 120 points into armour and MR based on the percentage of damage taken (eg. if you took 75% ad dmg and 25% mr damage, you gain an extra 90AR and 30MR)
Stats at 30 minutes mark: +300HP + (1-120) AR +(1-120) MR
Evolving Wepon: Evolution Stone + + 600 gold (total cost 3000)
Base Stats: 300 HP
Unique Passive: Adaptable Wepon. After 30 minutes, distrubutes 120 points into AD and AP based on the percentage of damage dealt (eg. if you dealt 90% physical and 10% magic dmg, you gain 102AD and 18 AP)
Stats at 30 min mark: +300HP + (1-120) AD +(1-120) AP
Pros:
- Really Strong late game
- Can be used for off meta builds as well as meta ones (eg.AP/AD shaco)
- It is possible to buy just the evolution stone, wait after 30 min and then buy the evolving armour/stone and get the stats that you would have gotten at the 30min mark
Cons:
- Very gold inefficiant pre 30 min mark
- If you want the item, you are forced to use 2k gold just for 150 hp otherwise you lose your chance of buying the Evolution Stone
- Even if you win the early laneing phase, your opponent will probably still be ahead itemwise if you choose to buy ES and they didn't
- Might force a farming playstyle early for junglers who might want to get it
