With 2 people you can Summon Doomcaster Suprax
it's far possible to only want 2 people to summon doomcaster suprax
warriors can soar from 1 rune to any other and trigger each of them
warlocks can use demonic circle
demon hunters can use infernal strike or methamorphosis
I have heard warriors being able to do it on my own as well, with the more heroic bounce legendary.
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You can summon it solo, just run onto each rune and it'll spawn. I've done this numerous times on multiple different characters.