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 42
Item Quantity Rarity GE market price Water rune 70 Common (~8/128) 350 Nature rune 12 Uncommon (~4/128) 2,556 Law rune 1–3 Uncommon (~3.5/128) 159–477 Fire rune 37 Uncommon (~2.5/128) 185
Item Quantity Rarity GE market price Green d'hide chaps 1 Uncommon (~2/128) 2,132 Green d'hide body 1 Uncommon (~2.5/128) 4,247 Mithril spear 1 Uncommon (~2/128) 281 Mithril kiteshield 1 Rare (~1/128) 1,028 Adamant full helm 1 Rare (~1/128) 1,864 Rune dagger 1 Rare (~1/128) 4,432
Item Quantity Rarity GE market price Toadflax seed 1 Uncommon 405 Irit seed 1 Uncommon 40 Belladonna seed 1 Uncommon 62 Poison ivy seed 1 Rare 25 Cactus seed 1 Rare 63 Avantoe seed 1 Rare 1,195 Kwuarm seed 1 Rare 605 Snapdragon seed 1 Rare 58,294 Cadantine seed 1 Rare 1,682 Lantadyme seed 1 Rare 2,547 Dwarf weed seed 1 Rare 697 Torstol seed 1 Very rare 51,115
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 17 Grimy marrentill 1 Uncommon 19 Grimy tarromin 1 Uncommon 179 Grimy harralander 1 Uncommon 598 Grimy ranarr weed 1 Rare 7,719 Grimy irit leaf 1 Rare 947 Grimy avantoe 1 Rare 1,945 Grimy kwuarm 1 Rare 1,266 Grimy cadantine 1 Rare 1,658 Grimy lantadyme 1 Rare 1,527 Grimy dwarf weed 1 Rare 513
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) 168 Shark 1 Uncommon (~3/128) 794 Ensouled elf head 1 Uncommon  2,005 Adamantite ore 1 Rare (~1/128) 1,242 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 557 Uncut emerald 1 Rare 759 Uncut ruby 1 Rare 1,351 Nature talisman 1 Very rare 708 Uncut diamond 1 Very rare 2,815 Rune javelin 5 Very rare 835 Loop half of key 1 Very rare 9,562 Tooth half of key 1 Very rare 9,737 Rune spear 1 Very rare 11,969 Shield left half 1 Very rare 65,555 Dragon spear 1 Very rare 37,310