Things You'll Need
Instructions
Complete the early Guild Hall quests to raise your character to Hunter Rank (HR) 6. There's no getting around this. You won't unlock the "Hunt Silver Rathalos" quest until you've reach this rank, which is the second highest in the game.
Upgrade a War Hammer to a War Hammer +, then a War Mace, then an Iron Striker, then an Iron Striker +, then an Anvil Hammer and then an Onslaught Hammer.
Go to the Guild Hall and accept the quest "Hunt Silver Rathalos." If you want, you can team up with another player to make this fight easier. Once you accept the quest you'll be taken to the tower.
Ascend the tower. You'll find the Silver Rathalos at the top.
Attack the tail until it falls off. Smash his head with the hammer next. Finally, focus your attack on his two wing claws. Once you've taken down these parts, he'll most likely have lost enough HP to die. If not, continue to bash him wherever is convenient.
Examine the Silver Rathalos corpse for loot including the Rathalos Rubies. You can repeatedly take the quest "Hunt Silver Rathalos" to accumulate rubies, which in turn enhance the Rathalos Soul Armor and the Rathalos Silver Armor.