Finishing up book 2 and

I still have no idea what is going on. Why the others want to stop Tal and have everything destroyed? Witch venerates are on his side? Nethgalla seems to want the barrier saved and so does Tal (I think?) but they are on opposing sides? Why El commanded Tal to do what he did? Why Tal is against doing that now? Basically just what is going on. I’ve always felt I had good reading comprehension but the motivations and twists in this aren’t making any sense.

Spoilers for book 2 are fine. I’m almost done at this point. Tal is fighting Melthier in the citadel and again I have no idea why.