They are not to be confused with Old Gnawbone, but you absolutely should soak in the knowledge and hold on to Mox Jasper, like a whelp, Young Red Dragon, or Dragon Egg
This was a state-based action bundled up with the triggered ability under the name of "Hideaway", but it has now been removed as of New Capenna
However, because of the immensely swingy nature of the game at the time caused by all of the extremely powerful cards that existed such as Monster Reborn, Raigeki, and Fiber Jar, destroying an opponents hand was oftentimes not enough to guarantee victory on its own
It's not a necessary part of the game, but it's certainly a fun addition
This is a perfect early game surprise for any challenge-focused decks, and with the option to have up to eight one or two ink cost Robin Shift targets in your deck, he should be nice and easy to play on curve
Modal spells have always been good because these cards allow you choose what you want to do based on the situation