This is a description of all the creatures in the deck:
Bounding Krasis: He's great as he can be Flashed in to tap down an oncoming attacker, or a blocker to help swing in once we've built up a board.
Den Protector: Usually unblockable for easy quick damage. It gets us back anything from our graveyard to recast like Reflector Mage, any of our Commands, or CoCo! Also is the best way to get Deathmist Raptor back.
Deathmist Raptor: 3/3 Deathtouch. Even if he dies, he comes back with a simple flipped up Morph like Den Protector or another Deathmist Raptor (remember that when Den Protector flips, a returning Deathmist Raptor isn't your choice of card to go back to your hand). He also combos nicely with Dromoka's Command's fight ability.
Harbinger of the Tides: Another great tempo creature to hit with CoCo. Combo's well with Bounding Krasis.
Reflector Mage: The ETB is just straight up value. Very cheap to play only costing . I'll totally bounce your creature and make sure it doesn't show up again until at least my next turn!
Eldrazi Displacer: This is where the Magic happens! This card is soooo good! Her ability allows us to blink any creature we want, so we can stop an attacking creature, we can save our own creature, or we can just blink one of our creatures like Reflector Mage and just get even more value out of the ETB effect of that or any of our other cards with ETB effects!
Sylvan Advocate: Probably the least impactful creature to hit with Collected Company. But late game he's a 2 drop for a 4/5 Vigilance. He also gives +2/+2 to our Lumbering Falls. All as long as we have 6 Lands that is.