In the previous article ranking the top blue cards in Modern, I talked about how the big difference between Modern and Legacy historically has been the lack of universal answers in the former, while the latter has cards like Daze, Force of Will and Wasteland
You can start the ball rolling with a 1/1 Lazotep Plating at the end of the opponent's turn to get them with a big Fireball-like effect (especially hot if you have two copies of Lazotep Plating)
A combo play like this can prevent a Casualties of War follow-up to Nissa which is usually game breaking
Phyrexian Arena is one of those, and youll play it whenever your game plan is to get ahead on resources, like to get an edge in midrange mirrors or to beat control decks
The ongoing trend of card advantage becoming less important than mana efficiency undermined their inherent appeal, especially when the evoke cost was still more than the median cost of spells in the format
As it happens, Archivist of Oghma and Deep Gnome Terramancer were both in the same set and both of them tend to play really well with a lot of the same cards