High priests have the same weapon attack as aligned priests along with a stronger kick attack, and can cast two spells per round from the full list of clerical monster spells. They have fire resistance, shock resistance, sleep resistance, and poison resistance.
The following information pertains to an upcoming version (NetHack 3.7.0). If this version is now released, please verify that it is still accurate, then update the page to incorporate this information.High priests are now referred to as "high clerics".
Four high priests are guaranteed to appear in the game: the high priest of Moloch that tends to Moloch's Sanctum, and the three high priests for each deity of the player's pantheon, who appear in their High Temples on the Astral Plane. In addition to those four, aligned priests can grow up to become high priests.
The high priests on the Astral Plane are always generated peaceful, and will remain that way unless you provoke them. The high priest of Moloch is likewise generated peaceful, but will become hostile once you enter the temple.
Like aligned priests, high priests are generated with a mace, small shield, 20–29 zorkmids, and one of the following cloaks: a robe (6⁄7 chance), cloak of protection (2⁄21 chance), or cloak of magic resistance (1⁄21 chance). Those generated normally within temples additionally receive 2–4 spellbooks, and their cloaks are uncursed if the temple is co-aligned with you and cursed otherwise. The high priest of Moloch will also have the Amulet of Yendor in their possession.
High priests are much more difficult to take on compared to regular aligned priests, due to powerful physical attacks and access to the full list of clerical monster spells, including paralyze, curse items and geyser. Thankfully, outside of grievous errors involving conflict on the Astral Plane or more dedicated extinctionist play, the high priest of Moloch holds the Amulet and is typically the only one you will have to actually fight.
High priest of Moloch
Players tend to save a wand of death charge for the purpose of killing the high priest of Moloch, as they present a major obstacle otherwise: Moloch will fire rays of lightning at you each time you attack his high priest, and the priest's melee-range attacks and clerical spells may spell as mentioned above. They can generate with a cloak of magic resistance and have an MR score of 70, with the cloak all but forcing you to get up close and personal regardless.
As mentioned above, the high priest of Moloch only becomes hostile once you step into the temple - in other words, killing them from the outside before they become angry is murder for lawful and neutral characters. Make sure you are prepared for the fight before opening the door, even if you plan to step back out and/or zap them with a death ray.
For players dealing with a magic-resistant high priest, a means of stoning them such as a footrice corpse or egg can prove a useful alternative. Otherwise, they should have a source of magic resistance on hand, as well as possibly half spell damage, to blunt or negate the impact of certain spells (e.g. paralyze and curse items). Summon insects will be a mild annoyance at worst, the blind spell is trivial to cure, and you should already have shock resistance and fire resistance to negate damage from lightning and fire pillar spells, though they can still destroy inventory.
The high priests are introduced in NetHack 3.1.0, which also introduces the modern Astral Plane and Moloch's Sanctum.
From NetHack 3.1.0 to NetHack 3.4.3, including variants based on these versions, covetous monsters' behavior towards the Amulet of Yendor could be exploited to obtain it from the high priest of Moloch: By luring a covetous monster such as the Wizard of Yendor or any of the demon lords and princes into the Sanctum, they would teleport to the high priest, engage and possibly kill them, and take the Amulet before warping back to attack you, all without you having to leave the vicinity of the staircase. The Wizard in particular was a reliable monster to use, since he would always appear twelve turns after you performed the Invocation; he could not actually damage the high priest, due to his Amulet theft attack is handled in mhitu.c, though he was still capable of stealing the Amulet. The was fixed prior to NetHack 3.6.0, via commit 9df113a.
Some 3.4.3-based variants retain the ability to have a covetous monster take the Amulet of Yendor from the high priest of Moloch. Other variants may replace or supplement them with a much stronger monster.
In dNetHack, the high priest of Moloch is replaced by the elder priest, who is far more difficult and can steal the invocation artifacts, as well as the Amulet if you obtain it from them. If killed, the elder priest can also quickly revive like a Rider.
In EvilHack, the high priest of Moloch is a racial monster like all other aligned priests and high priests, and may appear as a human, elf, orc, giant, drow, or illithid. They also guard a crystal chest containing a guaranteed magic marker.
Defeating the high priest of Moloch and obtaining the Amulet causes a gate to form in the inner Sanctum's west wall, leading to a previously unreachable part of the map that contains Lucifer and the portal to Purgatory. All other methods of leaving the Sanctum are suppressed and the up stair is removed, meaning that defeating Lucifer is necessary to leave.
For Infidels, the goal is instead to bring the Amulet of Yendor to the Sanctum along with their quest artifact, The Idol of Moloch, and sacrifice the Amulet to Moloch on the unaligned high altar - Moloch will then imbue the Idol with the power of the Amulet so that the player can invoke it on a specific high altar in the Astral Plane. The high priest of Moloch remains peaceful to Infidels, and provides one hint regarding which altar is the correct one (or both, if the Archbishop of Moloch is dead).