The exact nature of the trading system has yet to be revealed, but there are a couple of things that are likely to be true
(Need a refresher on how to play Lorcana?) Here well be running down the best action cards in Lorcanas debut set The First Chapter
When the second ability resolves, Endrek Sahr will be sacrificed regardless of how many Thrulls you control at that time, even if it's less than seven
You can set this up in the first few turns with Queen first, Nick Wilde Sly Fox Sleuth and the Queen damage ability on turn two, into Pluto turn three to play Queen again, setting you up for something similar turn four
One final issue to some degree is the mana base
However you plan to use sapphire in your deck, the characters below represent the best Lorcana sapphire cards in The First Chapter