This is a true Limited bomb! Basically, you have 8/8 stats for four mana, which is incredible for an uncommon card. Conclave Cavalier could easily be a rare card and no one would ever question its rarity slot. But here it is and ready to take both Limited formats with a storm.
The elf tokens also synergize very well with Siege Wurm and other cards with Convoke mechanic. This card alone puts the Selesnya guild in a very good spot this season.