Disabler is a generic term to describe a collection of potions, wands, and spells that have the effect of reducing a monster's capacity to fight effectively. Unlike many other games in the genre, disablers tend to be extremely effective and are an important part of any player's arsenal. Disablers typically inflict one of the following conditions on a monster: Stun, Confusion, Web, Blindness, Paralysis.
Stunning can be inflicted upon a monster using a wand of stunning or the Stun Ray spell. Thieves, Duelists and Beastfighters may also stun opponents on critical hits at high levels due to class powers. Weapons or arrows of thunder will also stun opponents, and thrown potions of cure poison will stun monsters with poisonous attacks. Stun rays tend to fail quite commonly because they can be both dodged and resisted.
Stunned monsters will stagger randomly. They cannot cast spells at the PC or use special abilities such as breath attacks, but can heal or teleport themselves.
Confusion can be inflicted upon a monster using mindcraft, thrown potions of confusion or potions of wonder. Mindcraft can be resisted by many monsters, and some are immune. Confusion due to potions is quite effective, though undead, constructs, and a few bosses (the ancient Chaos Wyrm as of 1.2.0) are always immune.
Confused monsters will stagger randomly. They will not cast spells or use other special abilities.
Web can be inflicted upon a monster by shooting a wand of webbing, casting the corresponding spell, or by using the webs generated by a spider.
Monsters stuck in webs cannot perform any action until they break free from the web. Note that monsters must walk into a web to be affected by it; shooting a wand of webbing at an adjacent monster will have no effect. Some monsters, most notably fire-based creatures, will break webs instantly. Others, such as dark elves and spiders, are immune to webs.
Blindness can be inflicted upon monsters by throwing potions of blindness, cursed potions of invisibility or potion of raw mana, or the Phial of Caladriel (humanoids only). Missiles with the 'of darkness' suffix will blind monsters as well. The acid blood corruption will randomly blind opponents which hit the PC in melee. Luring monster over light trap might blind them as well. Blindness is effective against many creatures including some undead and constructs.
Blinded monsters will stagger randomly. They cannot cast spells at the PC or use special abilities such as breath attacks, but can heal or teleport themselves.
Paralysis is a powerful condition that may only be inflicted using a wand of paralyzation. Paralysis bolts may be dodged, but are surprisingly effective against many powerful monsters such as the cat lord. All undead and constructs are immune to paralysis.
Paralysed monsters may not perform any action until the paralysis effect wears off.
Honourable Mention: Darkness Edit
Darkness can be cast by using the appropriate spell, a scroll of darkness or a crystal of darkness. Unlike many of the other disablers described here, darkness affects both the PC and the monster, so its effects are quite different tactically. In 1.1.1, monsters will stand around stupidly and allow the PC to kill them with ease, but this has been fixed in recent patches.
Monsters that cannot see in darkness will wander randomly. They will not cast spells at the PC or use special abilities such as breath attacks, but can heal and teleport themselves. Monsters who can see in darkness will behave normally.
Honourable Mention: Fear Edit
Fear can be inflicted by PCs who carry the unholy aura corruption or wear certain equipment such as the spiked armor of chaos and terror. Undead will occasionally flee from PCs with the natural enemy of undead intrinsic. Monsters may also flee of their own volition.
Fearful monsters will abandon their attacks and run away. They can be attacked continuously in melee as long as the PC can keep up, and as long as the monster is not cornered. If they are cornered (any square that they are able to run to will put them adjacent to the PC), then they will begin attacking again. Shooting missiles at a fleeing opponent will always cause them to attack, but spells and wand generally do not. Note that panicking monsters may also enter a blind rage, which can be quite dangerous.