It costs one more mana than Heros Downfall but will take out 98% of the things that spell will while also giving you scry 2, which is close in power level to drawing a card
If players have any cards in hand that allow actions to be taken with them from a player's opening hand, the starting player takes all such actions first in any order, followed by each other player in turn order
Champion is rather a beating when you eternalize it
Still, MTG players are a wily lot and the most insane skilled players will find a way to make this pop off.
If you have cheap utility dorks and useful things to do with pointless bodies (such as Recurring Nightmare or equipment) then Skirsdag High Priest is a potent tool, if not he is liable to not do anything
But it remains one of the most influential draw spells Magic has ever seen, defining card advantage for blue players ever since