The Leather Helm is a helmet made of Leather in Castlevania.
In Castlevania: Harmony of Dissonance, the Leather Helmet, it gives a Defense boost of +6. This is one more than a Cloth Helmet, but one less than a Sallet.
The Leather Helm is the most basic helmet found in Castlevania: Curse of Darkness. It can be created with a Bronze and Wild Memory and can be created as soon as you find the Weapon Combine skill in the Abandoned Castle. It gives Defense +2. The Leather Helm is the ancestor of all helmets that simply increase Defense by a certain amount that are likely to be the highest DEF boosting helmet in your inventory. Combining it with Aluminum will create a Corinthian Helmet, which doubles its Defense, which continues to double after each combination. Combining a Leather Helm with a Knight's Vein will result in a Gallic Helmet, which has Defense +10, and can be evolved to a variety of different Defense boosting helmets along multiple paths of evolution.
The Leather Helm can also be evolved into the only Helmet that increases Consititution by combining it with Ether to form a Ten-Gallon Hat (Con +10, Def +1). Combining it with Soft Leather Armor, Bronze, and Steel result in the special weapon Spike Shield.