The benefit of doing so is that when these time counters are all removed, you can play the card for free
It needs a shell, but I think itll find one in Standard, or create one
Battle Styles Master Set: 306 Cards, Checklist & Prices By Cardrake Research Team Updated What's in the Sword & Shield Battle Styles master set The Sword & Shield Battle Styles master set is 306 cards: 163 base + 123 reverse holos + 20 secret rares

Aesi, Tyrant of Gyre Strait Aethersquall Ancient Archipelagore Arixmethes, Slumbering Isle Awoken Horror Benthic Anomaly Benthic Behemoth Biblioplex Kraken Biolume Egg Biolume Serpent Bladecoil Serpent Bog Serpent Breaching Leviathan Brinelin, the Moon Kraken Caetus, Sea Tyrant of Segovia Charix, the Raging Isle Cryptic Serpent Deep-Sea Kraken Deep-Sea Serpent Deep-Sea Terror Denizen of the Deep Dirgur Nemesis Dreamwinder Eater of Days Famished Worldsire Floodtide Serpent Frilled Sea Serpent Gearseeker Serpent Glacier Godmaw Grappling Kraken Grozoth Gyruda, Doom of Depths Gyruda, Doom of Depths Harbor Serpent Hullbreaker Horror Icebreaker Kraken Iceridge Serpent Inkwell Leviathan Isleback Spawn Jokulmorder Junk Winder Kederekt Leviathan Kiora's Dambreaker Koma, Cosmos Serpent Koma, Cosmos Serpent Koma, World-Eater Kraken Hatchling Kraken of the Straits Krothuss, Lord of the Deep Kukemssa Serpent Lava Serpent Leviathan Lightning Serpent Loch Mare Lochmere Serpent Marjhan Monstrosity of the Lake Nadir Kraken Nemesis of Reason Nimbus Swimmer Pearl Lake Ancient Polar Kraken Reservoir Kraken River Serpent Ronom Serpent Rot-Tide Gargantua Sandbar Serpent Scourge of Fleets Scrapdiver Serpent Sea Monster Sea Serpent Segovian Leviathan

This should be enough information to help you figure out what sets your cards are from