Ancient Silver Dragon needs one successful combat hit to threaten a dramatic refill. When it deals combat damage to a player, you roll a d20 and draw that many cards. The ability also removes your maximum hand size for the rest of the game, letting you keep a large result rather than discarding back to seven at the next cleanup step.
The outcome is variable, so the deck should be happy with the flying threat and the possibility of a modest draw as well as the spectacular rolls. Haste from Lightning Greaves helps an eight-mana Dragon attack before opponents untap. Additional combats or double strike can create more opportunities to connect, but each requires a real damage event against a player rather than merely declaring an attack.
A large hand is most useful when you can convert it into a productive next turn. Mana rocks, low-cost interaction, and protection help avoid drawing many cards only to pass with no way to use them safely. The draw is not optional, so a depleted library can also become a concern after repeated hits or other draw effects. The no-maximum-hand-size benefit persists even if the Dragon leaves, once the ability has resolved. Choose an attack that can connect reliably, and treat the first hit as a resource swing that needs a follow-up plan rather than assuming the largest possible die result is required for the card to justify its cost.
