A elder brain only has 21 Int. A PC can have more.
And WotC decided it was too complicated to have long spell lists for monsters, so the psionic abilities of a brain got reduced to a short range mind blast, detect thoughts and dominate person once a day as per normal spell rules.
The brain is aware of all thinking beings in a 5 mile radius, but can only really influence them if they are in incapacitated.
There is a reason why elder brains are only challenge rating 14 in 5E.
Yes, but Netherbrain :P
I couldn't find a stat block for it. It took me to a page with a stat block for a Tarrasque with an Elder Brain in place of it's little peanut size dinosaur brain, which I will just assume is the same as a Netherbrain.
I would also accept a stat block for a Death Star with an Elder brain inside of it.
