Luden's Echo 6655since 10.23.1 23 changes
3400g (1250g base, 2380g sell)
Echo: Damaging Abilities deal an additional (100 + 10% Ability Power) magic damage to the target and 3 nearby enemies and grants you 15% Move Speed for 2 seconds (10s cooldown). Dealing ability damage to Champions reduces this item's cooldown by 0.5 second, up to 3 seconds per spell cast.Mythic Passive: Grants all other Legendary items 5 Magic Penetration.
Builds from: 
Lost Chapter
Blasting Wand
Builds into: 
Force of Arms
SpellDamageManaCooldownReductionMagicPenetrationAbilityHaste
Click any two patches to compare; the current range is shaded.
− (0s)Damaging Abilities fire 6 Shots that deal bonus magic damage to the target and nearby enemies. Remaining Shots fire on the primary target, dealing 20% damage.
+ Damaging Abilities fire 6 Shots that deal bonus magic damage to the target and nearby enemies. Remaining Shots fire on the primary target, dealing 20% damage.