Its third chapter and last ability is a board wipe (yes, in blue!), which destroys all creatures and replaces them with 2/2 Phyrexians
Its pretty common to lead with a Thoughtseize and crack a fetch, which makes it easy to flip Cecil quickly in the early turns
The fact that the lore gain from his ability is passive makes him even better than other cards with gain the lore only when they quest
Knowing the value can be vital for insurance if you have a valuable collection of MTG cards
Over time, Green got more card draw staples such as Harmonize and Garruk's Uprising, but White continued to be the game's weakest card draw color by a huge margin
Permanents that allow you to tap your lands for any color, like Cromatic Lantern and The World Tree, make it easier, but if you don't have access to these permanents early, you may be stuck on having the wrong lands for what's in your hand.