The rare drop table or RDT refers to two special drop tables of items. When slain, some monsters have a chance to give loot from one of the rare drop tables instead of loot from their own unique drop table. This chance usually ranges from 1/16 to 1/64. The rare drop table is shared by many monsters - examples are chaos druids, lesser demons, most Slayer monsters and the Kalphite Queen.
The rare drop table has three tables: the Standard rare drop table, the Gem drop table and the Mega-rare drop table. Most monsters roll the Gem drop table[1], whereas some higher-levelled monsters roll the Standard drop table. Both the Standard drop table and the Gem drop table have a chance at rolling the Mega-rare drop table.
The Mega-rare drop table contains mostly empty drops, but also the rune spear, dragon spear and shield left half.
It is possible to calculate the odds of a monster with access to the rare drop table dropping a specific item if the chance of them rolling the rare drop table is known. For example, fire giants have a 1/128 chance of rolling the rare drop table and the chance of a dragon med helm from the rare drop table is 1/128; this effectively means fire giants have a 1/16,384 chance of dropping a dragon med helm.
Some monsters will have their rare drop table drops appear on an adjacent tile to the rest of the loot pile when the rare drop table is rolled. This can help the player distinguish if the drop came from the rare drop table or their standard drop table, if both tables share some of the same drops.
Free-to-play players have very limited access to the rare drop table; they can only get uncut gems.
Talisman[]
Depending on the monster, when the Gem drop table or Standard rare drop table is rolled, the monster will drop either a Chaos talisman or Nature talisman[2]. Some monsters can drop either talisman if they have access to both tables, such as fire giants.
Gem Drop Table[]
Many low-levelled monsters roll the Gem drop table. The Gem drop table has a very small chance of accessing the Mega-rare drop table. Wearing a Ring of wealth will decrease the chance of receiving no drop from 63/128 to 31/96[3]. In other words, assuming a monster has a 1/16 chance of rolling the Gem Table, the Ring of wealth gives you one additional item from the Gem Table every 95 kills[4][5].
At current prices, the expected value of a drop is approximately 524.83, or 699.77 with a Ring of wealth.
[A 3]Item Quantity Rarity GE market price 
Uncut sapphire 1 Common
(32/128; 32/96)[A 1]455 
Uncut emerald 1 Common
(16/128; 16/96)[A 1]679 
Uncut ruby 1 Common
(8/128; 8/96)[A 1]1,249
Talisman
(Chaos/Nature)1 Uncommon
(3/128; 3/96)[A 1]Not sold
Uncut diamond 1 Uncommon
(2/128; 2/96)[A 1]2,627
Rune javelin 5 Rare
(1/128; 1/96)[A 1]875
Loop half of key 1 Rare
(1/128; 1/96)[A 1]10,307
Tooth half of key 1 Rare
(1/128; 1/96)[A 1]10,840
Rune spear 1 Very rare
(1/2,048; 1/1,536)[A 1][A 2]11,933
Shield left half 1 Very rare
(1/4,096; 1/3,072)[A 1][A 2]65,697
Dragon spear 1 Very rare
(1/5,461.33; 1/4,096)[A 1][A 2]37,226
Dropping monsters[]
Monster Combat level Quantity Rarity Gorak 145 1 Always Abhorrent spectre 253 1 Common (3x5/128) Shadow warrior 48 1 Common (1/16) Abyssal demon 124 1 Common (1/16) Ice troll runt 74 1 Uncommon (5/128) Gargoyle 111 1 Uncommon (5/128) Gorak 149 1 Uncommon (5/128) Aberrant spectre 96 1 Uncommon (5/128) Steel dragon 246; 274 1 Uncommon (1/32) Commander Zilyana 596 1 Uncommon (2/127) Sand crab 15 1 Uncommon Hobgoblin 28–47 1 Uncommon Minotaur 12; 27 1 Rare
Standard Rare Drop Table[]
The Standard rare drop table[6] tends to be dropped by higher-levelled monsters. It has a higher chance of accessing the Mega-rare drop table. It is considered to be the main drop table. It contains 128 slots. Note that within these slots, the Gem table has a weight of 20/128, and the Mega-Rare table has a weight of 15/128.
At current prices, the expected value of a drop is approximately 8,257.32.
Runes/Ammunition[]
Item Quantity Rarity GE market price
Nature rune 67 Uncommon (3/128) 14,539
Law rune 45 Uncommon (2/128) 7,470
Death rune 45 Uncommon (2/128) 9,135
Steel arrow 150 Uncommon (2/128) 4,800
Rune arrow 42 Uncommon (2/128) 2,940
Adamant javelin 20 Uncommon (2/128) 1,220
Rune javelin 5 Rare (1/819.2)[B 1] 875
Gems[]
Item Quantity Rarity GE market price
Uncut sapphire 1 Uncommon (5/128)[B 1] 455
Uncut emerald 1 Uncommon (2.5/128)[B 1] 679
Uncut ruby 1 Rare (1.25/128)[B 1] 1,249
Uncut diamond 1 Rare (1/409.6)[B 1] 2,627
Equipment[]
Item Quantity Rarity GE market price
Rune 2h sword 1 Uncommon (3/128) 37,758
Rune battleaxe 1 Uncommon (3/128) 24,487
Rune sq shield 1 Uncommon (2/128) 22,459
Rune kiteshield 1 Rare (1/128) 32,015
Dragon med helm 1 Rare (1/128) 58,488
Rune spear 1 Rare (1/135.13)[B 2] 11,933
Shield left half 1 Rare (1/270.25)[B 2] 65,697
Dragon spear 1 Rare (1/360.34)[B 2] 37,226
Miscellaneous[]
Item Quantity Rarity GE market price
Coins 3,000 Common (22/128) Not sold
Loop half of key 1 Common (20.16/128)[B 3] 10,307
Tooth half of key 1 Common (19.16/128)[B 3] 10,840
Runite bar 1 Uncommon (5/128) 12,368
Talisman
(Chaos/Nature)1 Uncommon
(3.47/128)[B 3]Not sold
Dragonstone 1 Uncommon (2/128) 11,932
Silver ore 100 (noted) Uncommon (2/128) 7,000
Dropping monsters[]
Monster Combat level Quantity Rarity Kree'arra 580 1 Common (8/127) Commander Zilyana 596 1 Common (8/127) General Graardor 624 1 Common (8/127) K'ril Tsutsaroth 650 1 Common (8/127) King Black Dragon 276 1 Common (1/16) Dagannoth Prime 303 1 Common (1/16) Dagannoth Rex 303 1 Common (1/16) Dagannoth Supreme 303 1 Common (1/16) Lizardman shaman 150 1 Common (1/25) Zulrah 725 1 Uncommon (1/32) Mutated bloodveld 123 1 Uncommon Fire giant 86; 104; 109 1 Rare (1/128)