Need help for a special item for a Land Druid

hey all,

I want to create a rare magic item for a druid that interacts with the choosen land type: arid, polar, temperate, or tropical. depending on what they choose, they would get an additonal benefit, until they choose another one.

for example, with arid they could empower their fire spells, or with polar they would be harder to grapple or restrain. I kinda don't have any thematic ideas for each of them.

thank you gang