Its a mono-white card, and the only mono-white assassin in the game, meaning Layla literally cant run a deck of entirely assassins without some heavy use of changelings
Playing Xorn on curve is a mistake unless you are creating treasure tokens by attacking with a creature like Hoard Robber, or are casting an Instant that turn which produces a Treasure token
Then, if its a Land card, you can put it into play tapped, and if its not, you get to draw it
When playing with the token copy cards specifically, token doublers are incredible
A build-around is of course pretty much what it sounds like, a class of card that rewards you for structuring your gameplan around it
At the beginning of combat on your turn, another target creature you control gains Haste and gets +X/+X until end of turn, where X is that creatures power