Although Marvel doesn't inherently do anything when it enters play without some setup, at four mana, players could take their time over the first few turns accumulating Energy counters with Attune with Aether, Woodweaver's Puzzleknot, and Aether Hub, so Marvel could eventually be activated on the same turn it's played for a potential combo win
Ideally though, you need to strike a balance between fuel and big old spells, and that makes cards like Avenger of Zendikar perfect for this kind of deck
We want to have multiple high-cost Characters in play, like Gecko Moria and Kaido, to present an attacking threat
Yes, you can have two of the same emblem active at once
Etched foil has been hit or miss ever since it debuted in Commander Legends