Using Fear, Horror and Madness: from the Ravenloft 5e conversion above (which are more or less the same as the ones in the DMG.
Powers Checks: These will not be known by the players regardless
Some spells may work differently, I will usually call this out to you when you select the spell, but if I miss it then I apologize in advance. In particular Detection and transportation spells are not as reliable, mind-reading/telepathy can lead to madness checks if used on the wrong creature.
Languages: Common is 'Mordentish' and to keep things moving, assume that is the tongue people are using, unless I tag otherwise.
In general I like to reward good role-play and will make full use of DMG options for combat options (and improvise further if required)