In Teferis case, it rewards you with a doubling effect on any card you draw beyond the forced draw of the turn which in Blue decks is very easy to take advantage of (or even abuse)
That flexibility is amazing, but goad is what makes this card
What this means is that basically any burn spell that would do more damage than necessary to kill a creature now converts that damage into direct burn, which is incredibly efficient
Lightning isnt a particularly exciting iteration of the concept, either
Delver of Secrets is great because it turns into a flying monster fairly quickly
Card Draw/Selection The new Core Set 2020 card Season of Growth seems like a great inclusion here since weve got a fair number of cards that target our own creatures, and even outside of that, weve got plenty of creatures we want to cast, so getting a free scry trigger sounds great