On your post-combat main phase, you can pay life equal to the number of players that were dealt combat damage this turn and draw that many cards
All of a sudden, many decks picked up powerful win conditions, especially as Celestial Colonnade and Creeping Tar Pit slotted right into control decks that needed more ways to close out games
Other Synergies and Combos Buster Sword + Cori-Steel Cutter it allows you to get trample and usually hit the player even when blocked, so you can activate the Buster Sword
As long as you arent plotting counterspells, though, this might be a nice way to get a card out of your hand for storm-style payoffs, to get the sweeper out on a turn when an opponent is tapped out, or to guard against discard spells
It's not a particularly strong effect, and other cards do what it does but better, but there's a novelty in Guardian Beast