Doctor Strange by Mark Waid Vol. 3: Herald
Doctor Strange: herald of Galactus?! When an alien sorcerer demands Stephen Strange's help saving his far-off planet from Galactus, the World-Eater ends up banished to the darkest depths of the mystic realms! Now Strange, his powers depleted, must undertake a rescue mission like never before! What effects will consuming other realities' planets have on Galactus? Dimensions are destabilized as the cosmic balance is upset, and now it's up to the good Doctor to make sure the World-Eater's bout of interdimensional indigestion doesn't destroy all that is! With a new other-dimensional feast and an unholy alliance, Galactus has never been more terrifying!
Collecting DOCTOR STRANGE (2018) #12-17.