Giving added value to creatures with ETB abilities is a very popular design space, which is why persist creatures have shown up in Commander and on the kitchen table since it was first printed
By casting your flash creatures at the end of your opponents turn, they will not have summoning sickness during your next turn, when youd cast them otherwise
Evasive characters can only be challenged by other characters with the same status, but Elsa, the Fifth Spirit comes ready with not only Evasive, but also the Rush effect
If the equipped creature is dealt lethal damage at the same time that you gain life, it will die before Excalibur II's first ability would resolve
Read More: Best Upgrades for MTG Rebellion Rising Deck
It also only has four cards in total when the most valuable Secret Lair always (so far) have had five or more