Mogul's Mail

artifact

+300 HP

Grants 1 Armor, 1 Magic Resist, and 5 Health when taking damage, stacking up to 35 times.

At full stacks, grant 1 gold and continue gaining 1 gold every 11 seconds.

Unique - only 1 per champion

Source

Artifact

What grants Mogul's Mail

Mogul's Mail enables

Armor

Armor is the physical-defense stat that reduces incoming Attack Damage (AD) damage.
Magic Resist

Magic Resist is the magic-defense stat that reduces incoming Ability Power (AP) damage.
Gold

Gold is the player-level economy resource.
Max Health

Max Health is extra maximum HP given to a unit.

Mogul's Mail scales with

Stacking In Combat

Stacking In Combat means a unit ramps its power within a single round.