It makes your army of goblins, elves, or zombies snowball quickly and is a must-have for tribal strategies in Commander
Summoning sickness prevents a creature from attacking or activating abilities that require tapping
Shalai and Hallar turns +1/+1 counters into damage, and this deck is full of ways to put them on creatures and overwhelm your opponents
Speaking of fixing your mana, Temple of Triumph, Temple of Abandon, and Temple of Plenty are great for that, and theyre very cheap
Although, at time of writing, we have only seen the box art, so this could be entirely misleading
This being an instant for two mana that also gives you more range as to where the damage can come from bodes well for it