Once Claire DLoon, Joy Sculptor enters the battlefield, for the rest of the game, all tokens you make are permanent cards, meaning if they were to leave the battlefield for any reason, they continue to remain real cards instead of disappearing
This means that by casting several spells, Hullbreaker Horror can be used to return several key cards to their owner's hand, setting opponents back to the Stone Age
If it has an ability that triggers "when you unlock this door," it will trigger when the Room enters
Moreover if you do the math, drawing many cards gives you card advantage and access to all other aspects of your deck more quickly, so you have greater chance to have access to more lands, ramp, removal, utility, creatures, combo pieces, even more card draw and any other strategy you may run in your deck
The instant four cost is a Murder and they lose life too, and then suspends
Or a flying commander