Heart swap location in Gaea Town

So there’s a heart swap location here, and from what i can tell, it is completely pointless.

what do i do with this?

It’s for a zygarde cell. Spoiler alert: You get to catch Zygarde :stuck_out_tongue:

ah, that explains it. I went to gaea town before doing the zygarde post-game event, so ill go back there. Thanks!