Legacy is an utterly huge format, and you can basically see the hallmarks of Legacy Prison in Death and Taxes in the form of mana control (in Thalia, Wasteland, and other cards), but there really isnt much in the way of successful Legacy Prison otherwise
It has a strong sense of identity
Plus, once you cast a big spell like Craterhoof Behemoth or Finale of Devastation, one of your creatures becomes an absolute monster
But it does cost three which makes it a good target for Trophy Mage
The ready effect can be useful but the lore gain is minimal and you also have to consider you need a location in play and to have a character moved there for this to even have a target
Even if youre not doing the thing with this and something like Kaervek, the Spiteful, it still makes all your opponents' things die to a sneeze