Since its a cast trigger, that spell doesnt have to resolve to get the energy, but that means you cant get it from other artifacts just entering the battlefield
Bitter Reunion Bitter Reunion is great in many scenarios but excels in reanimation strategies that use it to pitch their reanimation target, then crack it to give that creature haste
Transforming Etali, Primal Conqueror is mostly a last resort though, because why would you not want to keep casting Etali, Primal Conqueror to play all of your opponents' decks
On the other hand, in three-, four-, or five-color decks, playing any non-basic land that only taps for a single color of mana is a big cost
While we used to only get a single batch of Commander decks each year, nowadays almost every set comes with a varied selection of precons
When choosing cards for your deck, it's best to choose cards that work well with other cards in your deck