Contact Other Plane says:
You mentally contact a demigod, the spirit of a long-dead sage, or some other mysterious entity from another plane.
Does the caster decide whom they are contacting? Do they have to name someone specific? Or is it random, or at the DM's discretion?
Best Answer
The spell doesn't really seem to care who chooses or how it's chosen.
If the caster was meant to choose (a specific entity) it would be worded to say something like:
Or
If it was meant to be random it would be worded something like:
If it was meant to be up to the DM... Well you get the point.
As it is written I don't see that there's meant to be any one exact option so whether the players choose or the DM does, I'd say go with whatever makes the game more interesting and fun. Given that it's a 5th-level spell that can be cast as a ritual with a casting time of one minute (or eleven minutes) and only has the verbal component it's costing the party nothing but time (and maybe a spell slot) either way.