Har-Aken

Har-Aken, which roughly translates to "Holy/Sacred Kraken", is the final boss of the Fight Kiln Activity. It is a large monster with tentacles, filling nearly the entire area on wave 37, although its body is never seen. Its tentacles will continuously attack the player, with its head occasionally appearing. Only the head must be killed to defeat Har-Aken. The tentacles respawn rapidly, and will always be present no matter how many are killed. There are no safe spots, as they have been flooded with lava.

Tentacles
Har-Aken has a number of differing tentacles. Both types may attack with melee, but at a distance they will attack with either with Ranged or Magic, hitting between 0-25 even through protect/deflect prayers. They are level 800 and have 700 life points each. The head itself will not attack and will surface without the need to damage any tentacles.

Strategy
Har'Aken only attacks with his numerous tentacles. You can only defeat him by attacking his head. The head isn't always visible. It will rise from the lava for about 30 seconds before going back under for about 45 seconds. It will never appear on the north side of the arena, but it will randomly appear on any of the other three sides. It is possible to use melee weapons to damage it but it is weak to magic so polypore staff or storm of armadyl is recommended. Each time the head pops up, you will be able to hit it up to twelve times (whip speed and depending on how fast you are in spotting then attacking the head). It is also recommended that you stand in a corner of the platform, as there will be less tentacles that are able to attack you. You can also switch corners if you are being hit by both range and magic attack styles.

The use of a divine spirit shield or elysian spirit shield will also be very helpful in absorbing a lot of the Magic hits, also the use of the magic power-up crystal combined with the use of an Armadyl Battlestaff and runes kills Har-Aken in about 3 minutes, the crystal also helps with defending against the magic tentacle attacks, if you choose to use Protect from Missiles/Deflect Missiles. This is only recommended with a 95+ base magic level, as lower magic levels won't be boosted sufficiently high enough to defend the magic hits smoothly, even in ganodermic armour.

A safe approach to increase survivability without having to switch gear is to protect mage and wear melee armour with a high ranged defence such as Bandos armour or Torva armour. With 90+ defence, turmoil/piety, and overloads, there is very little damage taken from the ranged tentacles, and they can be dispatched quickly with any melee weapon, to prevent even more damage. The magic tentacles can be ignored.

To deal with the inevitable damage, a Pack Yak is recommended to have the most supplies possible by the time wave 37 is reached. A Unicorn Stallion pouch and healing aura scrolls can be useful to have after your beast of burden is emptied, since it is likely to be more valuable than two extra saradomin brew flasks(depending on how early you summon it and how many scrolls you use). High prayer is helpful for protection prayers. Protect/deflect range is recommended.

To have the best chance at getting to the final wave and defeating him, it is best to use all attack styles, and bring the best possible equipment available. It is said that fighting Har-Aken is easier than fighting two TokHaar-Jad, as damage from the tentacles can be mostly avoided with deflect/protect from range on.

The basic method is to attack tentacles until the head appears, then deal as much damage to it before it submerges back into the lava. It does not heal in any way, and you will simply need to repeat this method until Har-Aken dies. It does not have any other form of attack, but its true power is the duration of the fight, which can last a large amount of time and consume a large amount of supplies.

Trivia

 * Har-Aken is currently the second strongest monster in RuneScape, after Nex, as well as the strongest monster that must be fought solo and the strongest monster that does not use melee.
 * Har-Aken is a unique beast relevant to the TzHaar society, in that the majority of TzHaar creatures exhibit a reptilian or golem-like theme, whereas Har'Aken is based around the Kraken, a mythical giant squid. However, as the Kraken itself is seen as a lizard-like reptile in some legends, it could still fit in with the TzHaar's overall race.
 * Har-Aken could be the source of lava that turns the Tzhaar/TokHaar mountain into a Volcano, as the valves on the sides of it's face exude lava. This would further make sense as in the Elder Kiln Quest, TokHaar-Hok said that his race were made to specifically create mountains, there was no mention of volcanoes.