>>529917395
Seasons here are batches of newly released treasures/favorite items
>Season 1: Laplace, Exia, Frima, Diesel
>Season 2: Viper
>Season 3: Helm, Drake, Miranda, Milk
After season 2 they decided to change the release schedule to 4 every 6 months and the third season is ending soon. Helm is the only character of those 4 that isn't in the shop already. For most launch characters you can already purchase their dupes with silver mileage anyway in the regular rotating shop, so the other 3 are already in there and will stay around even when season 3 ends, so the only reason to purchase that thing is for Helm dupes.
Helm with her treasure skill kit is also arguably the strongest of any unit that received treasures so far, being used in campaign pushing teams, PvP, SR/UR, coop, tower, pretty much everywhere. If you don't have her at LB2 at least (which is required to unlock the treasure) I would recommend getting her there as it definitely will pay off.
But don't use gold mileage for it, those should be saved for new characters.