What it does
Wandering Spirit triggers when the holder is hit by a contact move: the attacker's ability becomes Wandering Spirit, and the holder gains whatever ability the attacker had. Both sides swap — it's not a one-way replacement.
Contact move identification follows the same rules as contact-dependent abilities like Tough Claws or Iron Fist — most direct physical strikes qualify, while ranged moves like Rock Slide and multi-hit distance moves generally don't.
The value here is targeted disruption. If you know the opponent's attacker relies on its ability — Swift Swim, Guts, Moxie — you wait for it to land a contact move on Runerigus, and that ability is gone. The attacker now carries Wandering Spirit, which does nothing for a dedicated attacker. Your Runerigus picks up whatever it got, and even if that ability isn't useful on Runerigus, the damage is done to the other side.
Wandering Spirit can't be Skill Swapped away or suppressed after the exchange — unless another contact move triggers another round of swapping.
Who runs it
Runerigus is the sole user (100%). Ground/Ghost typing gives it natural immunities to Earthquake and Fighting moves; its physical bulk is high enough to absorb a hit; its Speed is low but Wandering Spirit is a passive trigger, so going second doesn't matter for this ability.
Runerigus's moveset complements the plan: Stealth Rock to punish switching, Body Press to deal damage using its high Defense stat. Even when its job is to bait contact moves, it contributes to the game in other ways.
How to use it
Basic flow: switch in, let the opponent's attacker hit you with a contact move, swap abilities, then evaluate what you just got and adjust from there.
The key read is: which of the opponent's Pokémon most needs its ability, and how do you make it punch Runerigus? Some Pokémon are forced to attack Runerigus because of typing matchups. Others will deliberately avoid it once they know about Wandering Spirit — that forced change in behavior is its own form of disruption.
If the ability you absorb is useful (Speed Boost, Regenerator, something like that), stay in and use it. If you only wanted to strip the opponent's ability and your new one doesn't help, switching out leaves Wandering Spirit stranded on the opponent's attacker.
Tips & strategy
Wandering Spirit doesn't trigger on ranged physical moves. Rock Slide, Icicle Spear, and similar non-contact moves bypass it entirely. Against teams with lots of non-contact physical attackers, Wandering Spirit fires less often.
Protect + Wandering Spirit is a classic setup: scout a turn, confirm the opponent is using contact moves, then expose Runerigus to the hit the next turn.
In singles, Wandering Spirit is more predictable — one Pokémon at a time, no partner to redirect attacks to. In doubles, the opponent has more options to avoid triggering it, but Runerigus's presence still shapes how they play.