Light for the Necromancer.

In my opinion, summoning is still quite relevant in the late game, especially with high spell power, as raising the dead will be one of the most useful spells at the end of the battle. You can play as Vlad and he will raise a lot of troops. In general, in the late game, it's unlikely that anyone will switch from Darkness to Light, so you have to switch to summoning.

I don't argue, but there are also mines, frenzy, and other spells, and summoning is also very useful at the start. This magic is very dependent on the hero's spell power, which means that late game + summoning is still very relevant. Darkness magic: it is also good in the late game, firstly, mass spells, blind, and vampirism, etc., do not lose much of their usefulness in the late game. Light magic, by analogy with darkness, can also be taken in the late game, even for a necromancer. I think light + darkness for a necromancer in the late game is a very good combination.
And I would also like to express my IMHO regarding the question of ideology. You don't need to look at and tie the ideology of a race too closely to real battles, as originality is always welcome and helps to win battles.
For example, Light doesn't suit Necromancers (this is being discussed), and machines don't suit the Elves, but machines are a very useful thing for the Elves (you know why, I won't explain), and now, because of ideology, should they not be taken? You need to use all the ways to achieve victory (I think I went too far)...