OSRS: Why Does Saradomin Drop The Armadyl Crossbow?This post may contain affiliate links. If you buy something we may get a small commission at no extra cost to you. (Learn more).
The lore friendly answer is that Commander Zilyana stole the crossbow from Kree’arra, the Armadyl General.
During the God Wars, Commander Zilyana pretended to want to form an alliance with Kree’arra and stole the crossbow as a trophy. This is why (according to OSRS lore) Sara drops the ACB.
The gameplay reason for this drop is equipment balancing.
When the God War Dungeon was being developed by Jagex, they needed to properly balance the drops from each enemy so that no single general was too “overpowered” with drops.
They moved the Armadyl Crossbow drop to Commander Zilyana to balance out Kree’arra who already possessed an impressive drop table.