Vanguard

Vanguard is an Item purchasable at the Main Shop, under Armor.

Damage Block
Gives a 70% chance to block 40 damage if the wielder is melee, or a 70% chance to block 20 damage if the wielder is ranged.

Note that due to the way pseudo-random distribution works in Dota 2, the chance to block, despite being listed as 70%, is actually closer to 60%.