Draft:Monster movement

Omega 0.90.4

Monster movement depends both on the creature's abilities and on the destination. Flying, swimming, moving only through water, passing through solid obstacles and opening doors are different capabilities. Entering a square and surviving its effect are also separate checks.

Movement rules

Monster behavior explains when an awake creature pursues, wanders or retreats. Monster attacks explains the action interval and how movement can share an action with ranged attacks or nearby powers. This page covers the places a creature can reach and the effects of getting there.

Ordinary checked movement rejects a destination outside the map, the player's square, another creature's square or blank space. A creature restricted to water then rejects every destination whose terrain is not water, even if another ability would normally permit it. This restriction applies to movement, not to every possible construction or teleportation.

For example, the Elemental Lord of Water is restricted to water movement, whereas ghosts can pass through solid obstacles. Nazgul use spirit-like pursuit but are not intangible; having that movement pattern does not allow them to cross walls.

Terrain and doors

The following table describes ordinary checked destinations after the general restrictions above. Hidden doors are checked before their apparent terrain.

Destination	Who can enter	Important limit
Floor or open door	Any creature passing the general checks	A floor-looking square may still contain an unrevealed trap
Secret door	A door-opening creature, or an intangible creature	A door opener reveals the secret when its use is in line of sight; otherwise it remains secret
Closed door	A door opener opens it; others can try to break it; an intangible creature can pass even if breaking fails	Flying alone does not open a door
Wall, statue or portcullis	Intangible creatures	Flying and swimming do not substitute for intangibility
Water	Swimming, water-only, intangible or flying creatures	A water-only creature still cannot choose ordinary land
Lava	Fire-immune swimmers, intangible creatures or flying creatures	Fire immunity by itself is insufficient
Fire	Fire-immune or intangible creatures	Flying by itself does not pass this particular entry check
Revealed trap, hedge or abyss	Flying, intangible or confused-movement creatures	Confused movement also has a separate, more permissive path described below
Other terrain	Normally allowed by this destination test	Entering may still have an effect, and some player terrain effects have no monster equivalent

Door-breaking succeeds when a random roll from zero to one less than the creature's damage rating is greater than a separate roll from 0 to 99. It turns the closed door into rubble. The door-opening movement ability instead opens it directly. Doors can therefore delay a pursuer without being an absolute barrier, and a stronger damage rating can matter even outside melee.

After entering a square

For the player's timed inability to walk or jump, see Immobilization. A monster losing ordinary mobility to a trap has different recovery rules.

Normal movement places the monster on its destination and then applies that square's monster terrain effect. Flying and intangible monsters skip this entire terrain-effect dispatcher in 0.90.4, including its traps and altars. This does not make them immune to separately fired bolts, explosions or ordinary attacks.

For a non-flying, tangible creature that enters an affected square:

Effect	Result
Water or magic pool	Drowns unless swimming or restricted to water; monsters do not roll the player's magic-pool rewards
Lava	Dies unless both fire-immune and able to swim, including water-only swimming
Fire	Takes raw 0–99 fire damage, subject to fire immunity
Dart or pit trap	Dart deals twice difficulty in physical damage; pit deals five times difficulty and removes ordinary mobility
Snare	Removes ordinary mobility without ordinary HP damage
Blade or fire trap	Blade uses 7 × (difficulty + 1) minus the player's Def as physical damage; fire uses 5 × (difficulty + 1) fire damage
Acid bath	Raw acid damage from 0 to difficulty squared minus 1; zero at difficulty 0
Sleep gas	Removes wakefulness unless sleep-immune; leaves the old wake-up distance intact
Mana drain	Removes a directly assigned nearby shared-spell ability; does not indiscriminately remove every magical or ranged power
Teleport or disintegration trap	Uses monster teleportation or monster-targeted disintegration; these are not the player's trap rules
Trap door, abyss trap or abyss	Makes the creature vanish from the level, without the ordinary death rewards

These are the actual monster handlers. A hedge has no thorn or trifid handler in this dispatcher, even though ordinary creatures usually avoid revealed hedges. Likewise, a dart trap's player poison chance is not part of the monster dart effect. For damage handling, including the blade trap's possible negative amount, see Damage and immunity.

Losing ordinary mobility does not clear hostility or silence nearby powers. A snared or trapped creature can still attack an adjacent player or use another available attack route. Conversely, a sleeping creature may wake at its next action if you are within its unchanged wake-up distance; see Monster sleep.

Teleportation and forced movement

Ordinary random movement uses the creature's own destination restrictions, but confused movement uses a more general empty-space check. It can enter water, revealed traps and other hazards that the creature would normally avoid; the normal post-entry effects still follow.

The ordinary monster teleport routine requires an awake monster and selects a non-secret floor square without another monster. It does not use the ordinary swimming or water-only restriction, and directly places the monster rather than running the destination's terrain effect. Its floor search does not separately reject the player's square. A teleport trap can therefore relocate an awake monster in ways ordinary movement cannot. This search is also distinct from choosing any arbitrary visible square.

Other forced moves have their own rules. The chained Doberman death-hound can be pulled back to its tether point; blippers teleport through their nearby special ability and have no ordinary movement action. Vanishing, by contrast, removes a monster from play rather than moving it to a different square. It does not execute the ordinary death routine or supply its usual loot and experience.

Strategy

Use an opponent's actual abilities to judge a barrier. Water can separate you from a land-bound pursuer, but not a flyer or swimmer. A wall can block a flying Nazgul while failing against an intangible ghost. A closed door may buy time against an ordinary creature, but a door opener can enter directly and a strong creature may smash it.

Revealed traps are not a universal lure: ordinary pathing avoids them, and flyers or intangible creatures that do enter skip the terrain effects. Hidden traps and confused movement can produce different outcomes. A snare's loss of mobility is useful for creating distance, but standing next to the trapped creature still exposes you to melee.

Player levitation and riding use separate rules. In particular, the player's terrain dispatcher can still activate effects while mounted or when explicitly interacting with the square. Do not infer your own safety from the monster flight table.