So you want to travel across the wild wilderness. The travails of your travels depend largely on your light source. Stuff like food and maps is important too, of course- if you have a road or a river or some other very solid idiot-proof way of navigation, roll one fewer darkness die. If you aren't traveling and instead stay put (as most castles do) roll two fewer darkness dice.
These are not a replacement of random encounters, oh no. They are in addition- but they are also rolled once per trip, or for very long trips, once per change of lightsource.
Direct Sunlight- The most common time to travel. Helios looms overhead either for a short visit (or just as business as usual if you're in the Noonlands) and if any moonspawned monstrosities show their face above ground, they're probably going to get their shit smote. Your concerns will be other humans and maybe a pack of wild dogs or something. You can see a long ways, make note of landmarks, it's great.
Indirect Sunlight- Maybe there's a cloudy sky, or Helios is just a ruddy glow behind the horizon mountains, or you're beneath the thick canopy of a forest. Stupid and desperate monsters might come out in these conditions, though crafty ones know better than to tempt Helios. If you're traveling in this sort of near-night darkness, you should stick to roads and be sure you have torches on hand in case Helios drifts away. For those out in the Daylands, this is their standard and they are mostly used to it, though they prefer to only travel under the light of Helios when possible.
Roll a single Darkness Die for these travels.
Torchlight and other portable light sources- The light and law of Helios isn't around anymore. Whether you're underground, in a night phase of the Sunset Realms, or beneath a star-exclusive sky, you must realize that there is nothing between you and the dark but a small and feeble light. The kings of the securest castles still shudder when candles flicker in their chambers of stone, and people traveling by torchlight fear the unseen beyond their fires.
Roll two Darkness dice, so long as your lights last. If you have to venture beyond the light of a campfire for more wood, you're already in trouble.
Starlight- The stars, whatever they are, are distant and pitiless. Cold gleams of light on shiny leaves and gurgling water is all you might sometimes see apart from silhouettes and outlines, strange and terrible in this useless starlight. You are effectively blind when it comes to fighting and spotting things, but you can sometimes make out nearby movement and large objects.
Roll three Darkness dice.
Blind Dark- There is no light, none at all. Graves and caves are this dark. Even a second's exposure to this taints you until you are exposed to Direct Sunlight, and you roll an extra darkness die until this shadow is cleansed. But even a distant town, or a lone star, or an errant firefly, are enough to ward off actual darkness
You roll no darkness dice for extended times in this level of darkness, because the grues will get hungry before you do. A few hours is all you have. Maybe less, if you've been flirting with the darkness with teases of snuffed candles and hooded glances of flickering lanterns.
Moonlight- Moons aren't as bright as the sun and their light is often pale or off-color- it's hard to see color in Moonlight. Depending on the moon and your situation, traveling by Moonlight can be relatively safe, or it can be suicide. Moonlanders rely on Moonlight the same as Noonlanders rely on sunlight, and bold Daylanders sometimes set out in the light of a visiting moon for an early start, confident that Helios will arrive to chase off the offending moon and provide warm sunlight soon enough.
No Darkness Dice are rolled in Moonlight. Whatever their horrors, they are horrors of light, not dark.
1- Monster. If you're lucky, you've heard local information and it won't be a blind date with destiny.
2-Sign of monster. Two Signs in one journey indicate the monster appearing anyway
3- Lost. Could be mundane, could be warped space. Either way, you'll likely be rolling darkness dice again
4-Malevolence- Disease. Hronir. Evil shadows. Misplaced items. Mutation. Curse. Madness. That which lies unseen is ontologically uncertain.
5-Landmark- Something is here that wasn't before. A road leading off, a ruined tower, a gorge, stairs going down.
6- Local Color.