Guinsoo's Rageblade 223124since 13.14.1 8 changes
3000g (3000g base, 2100g sell)
Wrath: Attacks apply bonus damage On-Hit. Your Critical Strike Chance is converted into more.
Seething Strike: Basic attacks grant bonus Attack Speed, stacking up to a cap. While fully stacked, every third Attack applies your On-Hit effects twice.Mythic Passive: Grants all other Legendary items 5% Armor Penetration and 6% Magic Penetration.
Builds into: 
Seething Sorrow
CriticalStrikeAttackSpeedOnHitMagicPenetrationArmorPenetration
Click any two patches to compare; the current range is shaded.
− Basic attacks grant bonus Attack Speed, stacking up to a cap. While fully stacked, every third Attack applies your On-Hit effects twice.
+ Basic attacks grant 8% Attack Speed, stacking up to 4 times for a maximum of Attack Speed. While fully stacked, every third Attack applies your On-Hit effects twice.