At uncommon, Stinging Lionfish provides a free Twiddle if you jump through its hoop, whereas the rare Wavebreak Hippocamp provides the familiar excellent payoff of extra cards
Karn tries to use himself as bait, challenging Sheoldred to draw them out, but just as he's about to head into battle he receives word that a member of his inner circle cannot be trusted
Then he has trample and then a death trigger for an opposing Commander to be Ring tempted
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Standard has plenty of all three of those at the moment, so Barricade is a solid answer to bring in from the board
Understandably, secret rare cards have a much lower pull-rate (chance of getting, or pulling it from a product), and it is common to go through entire booster boxes without a single one falling into your hands