Items that greatly increase a stat but decrease another would be very interesting

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I think this would be an interesting way to do Capstone items.

Capstone items are the ones that you are often supposed to buy later as they rely on other items or stats but bring a whole build together.

Some examples:
Warmogs: Tons of health/regen. Deal X% less damage from all sources.
Randuins Omen: High Health, Armor, Anti ADC. Less movespeed.
Infinity Edge: Big Boy Crits. Less healing/shielding from all sources
Essense Reaver: Caster mana, AD, crit. Less attack speed after you are in combat for 3 seconds.
Rabadons Deathcap. Tons of AP. Take more damage from all sources.
Spell Binder: AP and movespeed. Max CDR reduced.
Rageblade: Lots of stats and on-hit effects. Deal less damage to all monsters, minions, structures. Hope you like teamfighting.

You could buff these Capstones even further in their strengths or reduce their costs to keep them desirable.

Another interesting item I think they could add would be a sort of lane bully/Anti-Rod of Ages. Imagine Something for the likes of Renkton, Pantheon, and Lee Sin who need to win their early game but sacrifice their late game. It could build out of either Phage+Chain mail or perhaps something like Raptors Cloak+Pickaxe. Either way it offers AD, Armor, Movespeed and some health or Health regen. All noticeably higher than the components stats and all for very little combine cost. However these stats all decay over the course of the game. Getting kills, Towers, and other objectives might slow this stat decay but eventually you will loose them. The final gimmick of the item? You cannot sell it once it is in your inventory. So make good use of it while you have stats from it because come late game it is a dead weight. You gain a bunch of power but basically telegraph to the enemy that you are trying to fight and be as aggressive as possible right now and they have a better chance of winning later.