for astralstones Q
https://alloder.pro/files/file/188-cartographer/
make a habit on before exiting the game visiting such a place and collect the stone
when you re-enter it you collect it also
this way you have 2 times a day a free chance of getting such a stone
if you dont want to do that you can buy these minerals from itemshop too
for soul devourer:
i recommend you just ignore this Q
(its some old raidboss or some thing, in the last time it seems this mob no longer spawns at all, i have visited this place a few times and did not find him
also, with level 50 he most likely would kill you anyway)