In 5e D&D + Grim Hollow, how does the 'undead' characteristic given to a human PC change how some spells, items or abilities affect him?
Grim Hollow is a dark fantasy content book and can be found here. Page 95 of the book handles the Specter transformation.
The relevant Grim Hollow's Specter transformation text is as follows:
You become undead in addition to any other creature types you are. [...] Spells that affect humanoids still affect you. However, you're immune to effects that only affect a creature of your new type of a specific CR. [...]
Will a cleric's Cure Wounds spell affect the Specter human with the 'dual' humanoid/undead type?
The spell doesn't effect undead creatures, but what about a humanoid/undead with the specific features mentioned above from Grimbollow? I read about the Centaurs' dual creature type (but not sure if it was changed to only 1 in the end) but I couldn't find an answer that seemed to satisfy the question.