Alloy

Alloy is the basic resource for crafting weapons (excluding premium weapons), armor, and cores in, introduced on October 5th, 2015's patch. Alloy can be obtained by killing bosses and scrapping Strongboxes. The amount of alloy varies based on the level of the character/team. Receiving mass bosses in Nightmare Mode, for example, grants the same amount of alloy as it would for an equivalent single powerful boss.

Trivia

 * Pickup sounds for alloy are shared with Grenade Crates and Turret Crates.
 * As alloy wasn't programmed efficiently, in any game mode (excluding non-alloy contracts) the alloy reward you receive is based on your level, your teammates level, the boss (provided it's killed) and any map alloy bonus boosts. As the value is predetermined (excluding in events), you don't actually need to pick up the loot, as long as the boss drops the loot and the game is successful, it gets added to your total alloy count.
 * In the Alloy Contract, the reward value that you'll get no matter how many zombies you kill or how much you collect, you'll always give a value that is roughly the same as your character level, or half to roughly the same game level if played on multiplayer.
 * Normally any loot drop from a zombie or secret room would count towards the High Damage Ammo skill pickup, however alloy does not.