Every Commander deck that cares about attacking or preserving its commander should be running a copy of Swiftfoot Boots if they dont have Lightning Greaves, and most decks can benefit from both
That's just scratching the surface, and it's worth mentioning that, even if it turns into another creature for the turn, Scion still doles out commander damage
Every upkeep, it fetches another curse to attach for free, like Cruel Reality or Overwhelming Splendor
The amount of mana you can contribute from your creatures is equal to that creatures power, so with sufficiently strong creatures, or one whose power scales, you can grab practically anything
This uncommon is a six drop 3/4 with vigilance that gives a two-toughness boost to everything you have, so it's a better Castle on legs
However, even just copying something like a Solemn Simulacrum for an extra bit of card draw and land ramp is more than worthwhile