Chance of an encounter

Anything above Terinyo, to the right of Terinyo, or both, will not produce encounters. Otherwise, by terrain type:

Water0%
Swamp18%
Road15%
Plains7.5%
Hills5%
Mountains3.5%
Forests2%

If you are Doomed, multiply by 5. If you are merely cursed (not doomed), multiply by 3. This is your chance per step of an encounter. Movement speed has no effect.

What will you meet?

If you have talked to Tywat Pare, no raider lords have been killed this game, are no higher than level 5 and have no more than 5000 experience, you have a 1 in 4 chance of the encounter being with Kranach, regardless of terrain.

NameCt 1Monster 1Ct 2Monster 2Ct 3Monster 3Ct 4Monster 4EscapeEscape 2
a group of roving raiders1raider lord3d4raider1d2goblin1d3kobold50%90%

Otherwise, if you are at least level 25, you have a 1 in 6 chance of meeting an encounter from the high level set. These are all equally likely regardless of terrain.

NameCt 1Monster 1Ct 2Monster 2Ct 3Monster 3Ct 4Monster 4EscapeEscape 2
a lone corruptor1corruptor20%75%
an entourage of chaos knights2d2chaos knight4d4chaos plague bearer1d6+2chaos servant50%80%
a group of horribly deformed beings2d4chaos mutant50%90%
a dark hooded figure1chaos wizard30%60%
a lone knight surrounded by an aura of hate and fear1chaos warlord50%85%
a black unicorn1black unicorn50%50%
an ogre army1ogre emperor3d3ogre lord2d2ogre magus10d6ogre40%40%
a herd of rust monsters1d2giant rust monster2d2large rust monster2d6rust monster20%50%
a quickling raiding party1d3quickling lord2d4quickling15%15%

Otherwise, if you are at least level 15, you have a 1 in 3 chance of meeting a group from the mid-level set. This set is subdivided into partitions of 2; the partitions are respectively for forest, hills, plains, roads, mountains, and swamps; randomly choose within each partition.

NameCt 1Monster 1Ct 2Monster 2Ct 3Monster 3Ct 4Monster 4EscapeEscape 2
Forest
a giant boar1giant boar30%90%
a wandering giant1fomorian giant90%95%
Hills
a hunting party of hill giants2d3hill giant1d3-2hill giant chieftain50%95%
a party of assassins5d4assassin0%90%
Plains
a horrible Dorn Beast1Dorn Beast80%95%
a wild air elemental1air elemental30%95%
Road
a party of assassins5d5assassin0%95%
a gnoll war party10d6gnoll10d3large gnoll1d4gnoll chieftain70%95%
Mountains
a warband of stone giants2d4stone giant1d3-2stone giant lord45%95%
a lone red dragon1red dragon80%20%
Swamp
a horde of plague bearers4d4chaos plague bearer60%95%
a lone black dragon1black dragon60%10%

Otherwise, the encounter will be from the low-level set. This is partitioned and chosen exactly like the midlevel set, except with 4 options.

NameCt 1Monster 1Ct 2Monster 2Ct 3Monster 3Ct 4Monster 4EscapeEscape 2
Forest
an orcish patrol3d4orc1d2+1orc scorcher1d2-1orc chieftain35%85%
a group of bandits4d3bandit1d2outlaw30%90%
a wandering brown bear1brown bear70%98%
a huge grizzly bear1grizzly bear40%85%
Hills
a pack of wolves4d4wolf1d4dire wolf25%55%
a hill orc patrol3d3hill orc2d2hill orc sergeant35%70%
an outlaw band2d4outlaw30%90%
a wandering wizard1black wizard80%50%
Plains
a large jackal pack8d4jackal1d6-4jackalwere20%80%
a hobgoblin patrol3d3hobgoblin1d2hobgoblin leader1d6-3hobgoblin chief40%95%
a roving barbarian group4d3barbarian1d3barbarian leader65%90%
a pack of wild dogs4d3large dog30%90%
Road
a group of outlaws2d4outlaw1d2outlaw leader20%95%
a pilgrimage of chaos monks6chaos brother6chaos sister75%95%
a skeleton patrol1d40+6skeleton30%90%
a lone necromancer1necromancer50%90%
Mountains
a lone stone giant1stone giant75%95%
a gnoll warband4d4gnoll2d4large gnoll1d2gnoll chieftain70%95%
a cave bear1cave bear60%95%
a pack of cave lions2d2cave lion30%90%
Swamp
a horde of lizard men5d3lizard man1d3cave lizard40%90%
a group of lost souls3d3zombie2d4ghul1d3wight1d2-1wraith15%50%
a horde of huge frogs3d3giant frog50%95%
a lone hydra1swamp hydra65%95%

Will I escape?

First you might be ambushed. You cannot be ambushed if you are invisible (regardless of the encounter monsters), if pass a Perception-1 in 100 roll, if you pass a 150 difficulty Alertness check, if you are a level 6 druid or a level 25 merchant (undocumented ability), or if you have the Scout talent and pass a 1 in 10 roll. Even if you meet none of those requirements, monsters only have a 1 in 30 ambush chance. They get an additional 1 in 15 if you are Cursed and a 1 in 8 on top of that if Doomed, for a combined ambush chance of 21% if cursed and doomed. If this happens, tough luck - you can't escape and the monsters start next to you, so no shooting.

Next, you get the chance to sneak. You successfully sneak (Stealth + Survival) times in 1000 tries. If you are invisible, you will successfully sneak an additional 500 - XL * 10 times (yes, XL hurts you here). Successful sneaking increases escape chances and allows you to spring an ambush of your own.

If you choose to ambush, a variable is increased by 50 times your Stealth skill and 30 times your Survival skill; this is probably the amount monsters are surprised in some way. If you fight or ambush, things end here.

You have five checks to escape an encounter. Only one of them needs to pass.

If you are a level 6 druid or level 25 ranger, you escape automatically.
An encounter's first Escape number is a flat chance of escape. This chance is tripled if you made a successful sneak.
If you are invisible, you get a chance to escape of the encounter's second Escape number. No tripling here.
Next, you escape if you make a successful Stealth check. The difficulty of this check is 200 minus the lesser of the escape numbers.
You will escape automatically 1/3 of the time with the Scout talent.

Failing all those: you have to fight.