While Morellonomicon is a good item for the AP, I'd rather have the MR over the small difference in AP. I would ONLY get Morellonomicon if the enemy has a lot of healers or if I'm behind (in which case, I build it out of Kage's Lucky Pick). Athene's Unholy Grail is a FAR better late item, letting you take better advantage of your CDR for a small increase in gold cost.
Nomicon isn't really a mana regen item. It is cheap AP and CDR.
I remember EG.Froggen always going Tear+nomicon in his early game core. Once you hit the mid game spike when you have seraphs+nomicon+deathcap you're super strong.
As far as I know it is still quite good cause of how tear stacks twice each 8 seconds instead of once every 3. That means you can get two stacks from clearing the wave with Q-E or E-R. Tear overall is quite slow to stack but Lux is actually not that bad.
Pretty sure that was before tear and seraph's were nerfed several times. I don't think it's worth building on her anymore; it takes too long to stack now.
The answer is athene's 100% of the time, every time.
While
I remember EG.Froggen always going Tear+nomicon in his early game core. Once you hit the mid game spike when you have seraphs+nomicon+deathcap you're super strong.