Drops, also known as Monster drops or Loot, are the items monsters leave for the killer when they die. Drops can be picked up by players. Drops often include bones, coins or other items. A lot of monsters have "100% drops", which is an item or items that are always dropped by that monster. 100% drops are more commonly bones or ashes. Certain monsters have more than one type of 100% drops. A good example of monsters who have more than one type of 100% drops are metal dragons, who drop bones and also, metal bars of the type of metal they're made of.
Large monsters (that take up more than one square) will always drop their drops in the south-westernmost square. This also applies to any Ranged ammunition that falls to the ground when ranging those monsters.
The player who has done the most damage will see the drop before the other players. If a player has done half of the monster's Hitpoints in damage, and the monster has had time to heal, someone else may end up doing the most damage.
A delay between the damage being done, and the creature eventually being killed, does not seem to affect the person who sees the drop first, as long as they did more than half of the total damage done.
In very rare occasion, when right-clicked the exact same moment as the monster dies, a screen may appear with the 100% drop only (and arrows if Ranged is used) and not with the other drops. Then, if right-clicked on the same spot again, the drops are present. This shows that RuneScape first lets the monster drop its 100% drop, and then quickly calculates the other drops and then they appear too. To improve the chance for this to happen, log on to a world with low ping.
All items have a chance of being dropped that is expressible as a number, their drop rate. Drop rates are not necessarily a guarantee; an item with a drop rate of "1 in 5" does not equate to "This item will be dropped after 5 kills." While each kill does nothing to increase the drop rate itself, it is trivial to state that more kills gives rise to more chance overall.
Given a known value of , the chance of receiving such an item times in kills can be calculated using binomial distribution.
The probability of receiving an item times in kills with a drop rate of follows:
For finding the probability of a obtaining an item at least once, rather than a specified number of times, we can drop the binomial coefficient and simply the equation to:
Where is calculating the probability of not receiving the item, and we use that to calculate the inverse.
Giving us the answer, we have approximately a 2.3% chance of receiving a visage during this task.