Elf warriors can be found in Lletya and parts of Tirannwn. They are featured heavily during Regicide. They are usually killed either as a Slayer task or to obtain teleport crystals which grant quick teleportation to Lletya. To unlock them as a slayer task, the player must complete the Regicide quest. 
Strengths and weaknesses
Elf warriors have high Defence and utilise strong weaponry - the level 108 warriors use a crystal halberd (which has the reach of a halberd but the speed of a whip), while the level 90 warriors use a crystal bow.
It is recommended to use high Prayer boosting armour (e.g. proselyte armour) whilst activating the Protect from Melee prayer when killing them. Players that have access to Lletya can easily recharge their Prayer at the nearby altar when needed.
Killing the elves in Lletya (which requires starting Mourning's Ends Part I) is more convenient than killing those in the Elf Camp as there is a nearby bank and an altar upstairs in the house where Arianwyn is located.
If the player has 43 Prayer, Protection prayers may be used while using the altar on the second floor at Lletya for Prayer restoration. The ladder is located north of the bank. Killing elves in Lletya requires starting Mourning's Ends Part I.
Some lower-levelled players may find that the safest method is to use Ranged or Magic while using the west bench as a safe spot. Note that the fences cannot be used as safe spots, and that the west bench is the only safe spot in the area. Note also that the elf warriors using melee have the same reach as a halberd, and so halberds should not be used by the player due to the fact that they are very slow. There is also a safe spot at the entrance of Lletya, just beyond the bench.
Another alternative to complete this Slayer task is to kill the elves at the Elf Camp. The Elf Camp has a fireplace and a fly fishing spot. Therefore, players can kill the elves there while supplying themselves with food through fishing. At the Elf Camp the elves can be safe-spotted with Ranged or Magic by attacking the ones wielding a crystal halberd and using one of the several stools or spear-walls at the camp. The moss-covered rocks cannot be fired over and do not serve as safe spots.
Another option available to those who have started the quest Mourning's End Part II is to kill the level 108 mourners in the basement of the Mourner Headquarters. As these mourners are considered elves, they count toward a player's Slayer task when killed. The level 108 mourners have lower defensive stats than ordinary Elf Warriors and so may be easier to kill. However, they do not drop seeds or ensouled heads. A slayer ring may be used to teleport the player to the nearby dark beasts. It may be a good idea to use the High alchemy spell here, due to there being frequent drops of green dragonhide bodies, chaps, and rune daggers.
Drops (Level 108)
Estimated drop rates are based off 1,000 kills.[e 1]
Item Quantity Rarity GE market price Bones 1 Always 72
Item Quantity Rarity GE market price Water rune 70 Common (~8/128) 350 Nature rune 12 Uncommon (~4/128) 3,240 Law rune 1–3 Uncommon (~3.5/128) 153–459 Fire rune 37 Uncommon (~2.5/128) 185
Item Quantity Rarity GE market price Green d'hide chaps 1 Uncommon (~2/128) 2,072 Green d'hide body 1 Uncommon (~2.5/128) 4,210 Mithril spear 1 Uncommon (~2/128) 264 Mithril kiteshield 1 Rare (~1/128) 1,005 Adamant full helm 1 Rare (~1/128) 1,833 Rune dagger 1 Rare (~1/128) 4,444
Item Quantity Rarity GE market price Toadflax seed 1 Uncommon 1,230 Irit seed 1 Uncommon 56 Belladonna seed 1 Uncommon 50 Poison ivy seed 1 Rare 18 Cactus seed 1 Rare 37 Avantoe seed 1 Rare 728 Kwuarm seed 1 Rare 484 Snapdragon seed 1 Rare 71,393 Cadantine seed 1 Rare 835 Lantadyme seed 1 Rare 1,865 Dwarf weed seed 1 Rare 446 Torstol seed 1 Very rare 53,909
Players have approximately a 14.5/128 chance of receiving a herb from this table.
Item Quantity Rarity GE market price Grimy guam leaf 1 Uncommon 8 Grimy marrentill 1 Uncommon 10 Grimy tarromin 1 Uncommon 101 Grimy harralander 1 Uncommon 498 Grimy ranarr weed 1 Rare 10,539 Grimy irit leaf 1 Rare 775 Grimy avantoe 1 Rare 1,600 Grimy kwuarm 1 Rare 1,264 Grimy cadantine 1 Rare 1,409 Grimy lantadyme 1 Rare 1,369 Grimy dwarf weed 1 Rare 500
Item Quantity Rarity GE market price Coins 20–440 Common Not sold Tiny elf crystal 1 Common  Not sold Teleport crystal (1) 1 Common (1/5) Not sold Bass 1 Uncommon (~4/128) 200 Shark 1 Uncommon (~3/128) 1,242 Ensouled elf head 1 Uncommon  1,975 Adamantite ore 1 Rare (~1/128) 1,069 Clue scroll (hard) 1 Rare Not sold
- ↑ https://twitter.com/JagexAsh/status/713721069136449537
- ↑ 2.0 2.1 In order to obtain this item as a drop, players must be killing the Elf warriors located in Lletya.
- ↑ Lv 108 elves drop the ensouled head at a rate of 1/40, while lv 90 elves drop it at a rate of 1/50. Not dropped by lvl 108 mourners.
Gem drop table
In addition to the drops above, this monster approximately has access to the gem drop table.
Show/hide gem drop table Item Quantity Rarity GE market price Uncut sapphire 1 Rare 447 Uncut emerald 1 Rare 680 Uncut ruby 1 Rare 1,276 Nature talisman 1 Very rare 755 Uncut diamond 1 Very rare 2,708 Rune javelin 5 Very rare 765 Loop half of key 1 Very rare 9,879 Tooth half of key 1 Very rare 9,767 Rune spear 1 Very rare 11,872 Shield left half 1 Very rare 65,481 Dragon spear 1 Very rare 37,492