Originally posted by Fulmir:

It says it buffs or supports allies, but there's no buff icon and no real explanation I can find of what sort of support it provides. Is there a wiki or similar, or can I otherwise get an explanation of what the Sentries do?

Every few seconds the Totem Sentry will automatically inflict a hit of damage on all enemies within its radius (as indicated by a circle made of dusts).
When the Totem attacks, it will swap between 4 colors; Red, Purple, Blue, and Yellow.
Depending on what color it is, the Totem will passively apply a different buff to players and enemies within its range;
Red: Gives players Wrath, and enemies Hellfire
Purple: Gives players Swiftness, and enemies Shadowflame
Blue: Gives players Endurance, and enemies Frostbite
Yellow: Gives players Regeneration, and enemies Ichor

As for a wiki, there currently isn't one, but it's something I'd like to try doing in the future. It'll be a huge undertaking, though.

P.S. sorry for the late response, I didn't notice this discussion pop up, as steam doesn't notify me when that happens.