The drop event (Lapras-ex) should be at the top
And since elf decks are packed with cheap mana-producers, your board fills out quickly, meaning that game-ending drain can come online sooner than your opponents expect
In addition to this, the sets Umbreon has been included in are often limited releases, like Prismatic Evolutions in 2025
Whenever this creature or another creature you control is turned face up, that creature deals damage equal to its power to each opponent
While "Stromberg" already has several advantages by its summons alone let's not forget its battle coverage, as pretty much nullifies the opponent's attacks if they don't wanna lose monsters in vain
You could pick this early and try going mono-black, but I dont even think Zodiark looks good enough to stretch to that