Melee attack - The demon swipes at the player, which is a single targeted melee attack.
Magic attack - Single target. The demon fires a ball of grey sludge at the player. When praying Protect from Magic/Deflect Magic, this will drain prayer points instead of dealing damage.
Portal attack - Har'Lakk opens three different kinds of portals with a 3x3 area effect, resembling coloured rain. They can be avoided by running away from the portals. All portals disappear after a period of time.
A flame portal will flush you out! - Coloured orange. The damage begins at 5% of the players' maximum life points and increase by that amount every tick spent in the area of effect. Running away from the 3x3 area will stop the damage, but the damage will have retained its increasing strength if the player runs back into portal.
Taste miasma! - Coloured purple. They will inflict poison on the players that increases in strength the longer they stay within the targeted area. The poison will be instantly cured upon Har'Lakk's death. In free-to-play worlds, this portal is identical to the flame portal.
This will cut you down to size! - Coloured black. These will drain almost every skill level, most importantly the combat stats.
Prayer-disabling attack - Har'lakk will sweep his arms together, dealing two typeless hitsplats on all players around him in melee range and disabling protection prayers. Har'Lakk will only use this special when a player is standing under him or seems to be only one square away, the normal melee distance being two squares.
Har'lakk was originally purple and resembled K'ril Tsutsaroth before K'ril was updated. However, after the warped floors update on 2 November 2010 he was redesigned, along with To'Kash and Bal'lak, to a newer form, the same style as Yk'Lagor and Kal'Ger. He was updated again, along with all other demons, on 28 January 2013 with the release of Demon flash mobs.
After the release of the Occult floors, his icon tabs were updated to a newer image, an early hint that the Kal'Gerion demons would receive a graphics update.
Har'Lakk was potentially the most poisonous creature on RuneScape before the Evolution of Combat. His poison could potentially deal over 900 damage if allowed to accumulate long enough. Unlike the previous record holder, K'ril Tsutsaroth, Har'Lakk was not initially immune to poison. A hidden update changed this and gave Har'Lakk immunity to poison.
Even after the demon was killed, it was possible to take damage from the portals and even die from them. This was fixed with the release of the Demon Flash Mobs.
Har'lakk the Riftsplitter is the only Kal'Gerion general to not be the final boss of a floor theme. This role is assumed by Night-Gazer Khighorahk.