Anywhere there is power, there are Strangers. As such, everyone has been instructed to be vigilant. Most PCs who have put any effort into learning their Strangers will have the following knowledge:
Hellions are red-faced, dangerous and powerful. They tend to have horns, carry threatening weaponry and often have the capabilities to prepare Magical Items, which they “reward” their human servants with. They are obsessed by the gathering of Power, through trade, and have been known to demand sacrifices or worship in this aim. When an average person thinks of a Stranger, it is an image of a Hellion they have in their mind.
Phantoms are a form of Sprite left behind at the sites of great battles, haunting those who return there. There are known cases of phantoms killing looters and arranging their bodies in horrifying positions to discourage further desecration They are fairly intangible, the fluid, congealed properties of their essence making them highly resistant to weaponry, but their substance is quickly distorted by concerted effort or by Magical power.
Golems seem to have no defining purpose. They tend to be tough, regardless of what they appear to be constructed from, which varies wildly from example to example. They tend to respond to nearby Life by striking it to the ground and continuing to smash against it until it stops moving. These are extremely rare- maybe four or five reported cases in the past decade, but reports from Mat Sellah’s first scouting parties of all Factions have reported Golems roaming areas of the countryside. This is especially concerning because Golems, once their physical form is destroyed, tend to reform and return to their previous habits- killing anything nearby.
Sprites, in general, are Strangers seemingly in tune with a particular place and emotion. They are unpredictable, ranging from malicious to benevolent, and often reform after discorporation.
This is not to say that that was an exhaustive list of Strangers, simply ones which have been observed to have features linking to them, making them in some ways more comprehensible. There are many Strangers out there with only the vaguest resemblance to each other.