So I notice in Slipperiness Spell and Oil of Slipperiness it says that to stay standing you need to make a ‘Proficiency Throw’ of 20+
What does that mean exactly? I mean, clearly they need to roll a 20+ on the die, but what can you add to that to get a 20+? What proficiency adds to the roll?
There are some abilities (such as the race power of Dwarves) that increases all your proficiency throws. So a Craftpriest would only need a 16+
Kinda sounds like it’s an Acrobatics proficiency check - that throw starts out at 20+.
Moreover, the Dwarven Craftpriest’s ability only works with Proficiencies that they learn. Hence, it wouldn’t apply here.
As the spell doesn’t call out a specific Proficiency, I can see numerous ways of ruling on this. One would be to go with Acrobatics, as suggested above. Another would be to assume the Throw could be modified by Dexterity. Finally, one could assume there’s no modifier, and the spell makes things almost perfectly slippery, meaning everyone needs a 20+ to avoid falling down. If going with the latter, I’d probably also assume they can easily slide out of the area if they can find anything not-slippery to push off on.
Yeah, I agree there is a lot of ways to read it. I’m just thrown by using the prof designation because it seems like something was meant by that. Should level effect it? What about monsters who don’t have profs?
My players are using it tonight in the game… need to figure it out!!! 
Personally, I’d assume nothing (maaaybe Acrobatics) affects it. It’s a touch range spell with a 10’ x 10’ area - it’d better work! Mages less than 10’ from something nasty are very, very squishy. If it’s laid in advance (and the target is walking - I’d expect runners to fall and slide out the other side), that’s clever play by the PCs and should be rewarded by being effective.
I didn’t intend anything special by the term – Proficiency throw is simply the default verbiage I employ for actions in the game.
I think allowing characters to use Acrobatics proficiency to avoid slipping and falling seems very reasonable.