This is a great way to dip your toe into the water if you aren't sure the Prerelease is something you want to do or if you can't commit 5 hours to a Prerelease event
Do you have a favorite reprint
Enter Giant Killer, who we can cast the adventure side of to get rid of a big threat, and then cast the creature side and keep something at bay, fits that nicely
So, Dragalge EX effectively does anywhere from: 110 DMG (with Darkrai EX) 120 DMG (with Darkrai EX and 1x Nihilego) 130 DMG (with Darkrai EX and 2x Nihilego) Since its already equipped with Poison Barbs effect, you can give it Rocky Helmet for an additional 20 DMG
Trainer is often killed on sight even with a smaller emphasis on the otter synergies
If your opponents snipe Ureni with a removal spell, you get to cast it again and keep getting dragons, or just use the dragons you already obtained