For sure, its going to be a chase card for those picking up Journey Together, and its value will likely go on to reflect this
While Slifer the Sky Dragon might not be as strong as The Winged Dragon of Ra, it's no less iconic, being a huge aspect of one of the show's most impactful arcs
You play Abrupt Decay when you feel fragile in the early and mid game, when your outs are a bit long winded and expensive and when your low end is all set up rather than pro active or reactive
He's going to draw you some cards when he comes down, and once he transforms he kills something, attacks as a 9/9 on the next turn, and gives you a bunch of mana
Past Magikarp cards have done really well overtime in value, so this might be one to hold onto for a long time