The Spells Wild Slash gets the maindeck nod over Fiery Impulse because you want to be able to cast it at any time to get value out of your Prowess creatures, most importantly Monastery Mentor
The card wasn't corrected in the regular Revised print run, so despite its notoriety, it's not particularly valuable
Adding Threats On the flip side, you can also use your sideboard to find a new threat that your opponent will struggle with
This card can counter all other spells, switch each creatures power and toughness until the end of the turn, or make all creatures unblockable until the end of the turn
Its a two-mana 1/1 that gets a +1/+1 counter on it as long as it has fewer than three +1/+1 counters on it
For sure, although it will be far from the best draw in the deck