I did that fight recently with wiz, warlock, sorceror, cleric. 2 Ice Mephits and a Shovel, everyone staying near portal.
Started Hunger of Hadar left side approach
Fireball at front/right baddies
Sleet Storm added to Hadar on left side
Spirit Guardians up
Finish off the bad guys coming from front/right however, nothing getting through from left, all trapped in icy darkness. If anything does get through blast them back into the dark with Eldritch.
Add Wall of Fire to left for the lols.
Nuke them all down and had 2 turns left for portal with all enemies dead.
