The icon differs from Elden Ring Items other buffs:

Diamond background = Temporary consumable/weather rune buff
Square background = Passive Gold Scarab Talisman rune buff

Multiplayer Group Buff Variant

This buff can also trigger in multiplayer when you use a group password:

If anyone in the group defeats a Shardbearer or becomes Elden Lord, everyone in that group (sharing the password) will receive a temporary rune acquisition buff.
This is separate from the weather event, but shares a similar icon and effect.

If you're part of an active multiplayer group, especially a large one, it's possible to have this rune buff up fairly often, even passively.

Gold-Pickled Fowl Foot - How to Get More

You can craft them once you get Missionary's Cookbook [2] from Patches, requiring:

3x Rowa Fruit
1x Four-Toed Fowl Foot
1x Gold Firefly

Alternatively, you can buy Elden Ring Items or find several throughout the game.

Summary: How to Boost Runes Efficiently

If you're hunting runes or farming for levels, here's your optimal setup:

Equip Gold Scarab Talisman
Use Gold-Pickled Fowl Foot or Golden Horn Tender
Look out for Erdtree Leaf Storms at night
Join a shared multiplayer password group to get communal rune buffs

Whether you stumbled upon it by accident or tracked it down intentionally, the Erdtree storm is one of those rare Elden Ring moments that reminds you just how layered and buy Elden Ring Runes mysterious the Lands Between truly are.