So, things have been pretty rough lately, but I am back... Im ready to continue things in Tristan, alone apparently... So I guess, can anyone tell me the maximum level of size for a dark portal?

That is, the equation that lets you know the max size based on your post count.

Dark Portal "strength" depends on a few factors, including post count/life force of the user, ambient dark energy to draw from in the area, size of the portal, distance traveled by the portal, and number/size of the object(s) put through it.

Assume a beginner Dark Mage could teleport him/herself around with a 1/5 sacrifice (using rough estimates), and that a Dark Mage like Siege's Morganus character could use Dark Portal to move a small town many miles.

Without falling down dead, you could probably move many hundreds of people, or equivalent mass. That would probably expend most of your energy. Siege would be a better person to ask, or even Ezekiel. I'll see if I can poke around and fine Siege for you.

I am not the one to ask cause I will standby the normal, dark portal follows the same rules as teleport.

I also don't want to go into great detail on the size of said portal, honestly size doesn't matter the question is how long you need to sustain it. One of those you can make a huge portal fairly easily, maintaining it long enough to move whatever you are thinking of is a entirely different matter. That said I would assume you would steadily grow weary while holding the portal open, the larger the portal the more energy the faster you kill yourself.

That said size wise go off what Luthe said, I would also double check and see if you can bypass the whole you can only teleport yourself deal. (( this should be easy enough it has been done in the past))

my basic idea was to use the dark portal to redirect the massive ball of holy... although, I'm not sure how magic interacts with each other or if the dark portal could even move a holy attack...

Light attack yes, if said holy attack works like holy it will simply nullify the dark portal.