Hi
@ReverseConcaveSpoon
I hope you are still reading the forum. Don't worry about the experience you had. I'll explain why you shouldn't.
I once read the report of a person on a forum. Every time this person smoked Salvia divinorum, he found out that they were a carpet hanging on a wall and that in front of them there was an elephant head, and that it was the real world, while everyday life was an illusion. Does it make sense to you that we're carpets hanging on walls staring elephant heads? You should take your experience with the same scepticism.
Let's suppose you visited a really existing place (like another dimension). Maybe those entities were just making fun of you. Or more probably IMO, you were just confronted with one of your fears.
Now talking about this fear or anyway this thought that frightens you, that only you exist and it's all an illusion. This can't be the ultimate reality. Because ultimate reality goes beyond all mental concepts, and "Only I exist" is a mental concept, an extreme. "Oneness", "multiplicity", "existing", "non-existing" are among such extremes or mental concepts. Reality is beyond all of them. So don't worry about only you existing. That's not the truth.
And don't think that those entities were right just because that realm was hyper-real. The hyper-realness of a realm doesn't mean that the entities you see in it are real, or that they tell the truth. They can be just manifestations of your mind, of your fears.
In that state, you have the potential to recognize your true nature, but only if you are not distracted by the projections of your mind, by your fears. If you manage to keep your firmness against those entities and what they say, and tell them "I know you are just manifestations of my fears inside my own mind", believing your words, they will disappear just like they have appeared, and the nature of your mind, the nature of reality, will shine, and you won't fear anymore. You don't have to take DMT again to do it, you can do it in meditation.
Meanwhile, enjoy life on Earth knowing it isn't an illusion, and that the light of the nature of reality shines through it, even when you can't see it.
Take care and don't worry