D'Sparil is the final boss and chief antagonist of Heretic, and is boss of Episode 3: The Dome of D'Sparil. He is the first and the youngest of the trio of Serpent Riders, using cunning and deception to initially gain dominance of Parthoris, the world of Heretic. He declared the supernatural race of the Sidhe to be forever hunted as heretics to their new Order. The Raven sequel, Heretic II, begins with D'Sparil's death and shows D'Sparil cursing Corvus.
The name "D'Sparil" almost certainly comes from one of id Software's earliest games, The Catacomb (1990); level 12 of this is called "The Tomb of Desparil".
The player, as Corvus, fights D'Sparil in a wide arena with a large trident-shaped ledge in the upper-middle, and various teleporter destinations scattered around the map. D'Sparil initially is seated upon a Green Chaos Serpent, which are prevalent in Hexen.
The Serpent is the most powerful of any Chaos Serpents in the series itself, able to belch fireballs, at first in single units, and then after falling below half its Health, shoot a line of three scattered fireballs at the player. The Serpent can also make a bursting charge of speed towards the player when stunned by attacks. Like the Iron Lich and the Maulotaur, D'Sparil is immune to the effects of the Morph Ovum and cannot be instantly killed by the Firemace under the influence of the Tome of Power. D'sparil also has a 50% immunity to the powered up Hellstaff's rain like the Maulotaur.
When the Serpent dies, D'Sparil will electrify and rise up, and start attacking the player. His abilities are a mix of offensive and defensive tactics, one being to fire a blue, trailing bolt of electricity for extreme damage to unarmored players. He can also shoot a pair of purple rings which turn into Disciples of D'Sparil, and teleport himself to one of the 6 raised platforms in the area. As he is damaged more, he will teleport more often. D'sparil will also often teleport when he is hit by a Phoenix Rod missile or Hell Staff rain (the game code does a specific check for these weapon hitting him).
When D'Sparil finally dies, he explodes into a pile of bones in a burst of electrical energy, all the other enemies on the level will instantly die, and the portal to the end of the third episode will be revealed.
D'Sparil's entire fight is 5500 Hit Points; 2000 Hit points for the Chaos Serpent, and D'Sparil himself having another 3500 Hit Points.
First off, run all around the large arena, collecting everything you can, including the Wings of Wrath. Fly to the ledge above, there are plenty of Mace Spheres, as well as two secret doors, one on the far end of each side, containing a Mystic Urn and a Ring of Invincibility; at this point D'Sparil should rarely if ever even attack you until you start fighting him in earnest. Now pay attention to D'Sparil. Use the Phoenix Rod from a distance and you should be safe, but be aware that the Serpent will start to run and fire more fireballs the weaker it gets (by this point in the game, you should have no trouble circle strafing). When D'Sparil rises, his only attack is a fast lightning bolt that deals massive damage but gives you plenty of warning, but the real challenge comes from his teleporting around and summoning Disciples; you should eliminate him as quickly as possible since the Disciples he summons may annoy (or kill) you. The Hellstaff might be an option to kill him, but consider the Phoenix Rod as well - D'Sparil teleports rather often so slower projectiles from too far away and continuous attacks won't work so well. If you've got a Firemace, it won't be so hard for you, and if the Disciples he summons get out of hand, consider using a Tome of Power with the Dragon Claw to clear them out. Good luck.