Leaf is a Diablo 2 Resurrected runeword created by combining tir + ral into a 2 socket staff. It requires at least level 19 to equip.
Leaf is particularly good for Fire Sorceresses for its +3 to Fire Skills. However, the Fire Skill bonus is not limited to Sorceresses, so this is also a great early-game option for Fire Druids. When used on a Sorceress, the runeword can be augmented when created in a base that already has a bonus to skills.
Potentially giving +9 to Warmth, which is very useful for a starting Sorceress, struggling with Mana regeneration. The bonus to Warmth will only beneft Sorceresses, as it is a class-specific skill bonus. Keep in mind that synergies only work for hard skill points, so the +3 to Fire Bolt will not benefit you when you transition to Fire Ball.
Staves can have up to 3 auto mods specific to Sorceress spells ranging between +1 and +3 to skill level. Therefore, you should look for a 2 socket staff with at least some +skills that your build uses. An easy way to quickly find good staves is to shop with Drognan in act 2. You can reset his shop by exiting and re-entering town.
Did you know? It takes on average 4 countess runs on Normal difficulty to get this runeword.