Unburden
Speed is doubled on held item loss; boost is lost if it switches, gets new item/Ability.
Pokemon with Unburden
Using Unburden in Cobblemon
Abilities take effect when their particular conditions are met. If Unburden is marked hidden on a species above, its availability depends on the server: servers differ in whether hidden abilities come from breeding, an Ability Patch, or events.
See the Pokedex for which abilities each species can have, and IVs, EVs and breeding for how to actually pass one down.
Battle summaries use the Pokemon Showdown Generation 9 reference. Species associations come from PokeAPI. Custom server mechanics and mod versions may differ.