It's generating resources, in this case a creature
Legendary Creature - Elemental Phyrexian Sea-Dasher Octopus Mutate (If you cast this spell for its mutate cost, put it over or under target non-Human creature you own
As was the case in their original debut, these two new cards are designed to work together , granting one another buffs such as increased attack power and the Ward buff.
It can provide acceleration in almost any way possible, and is generally revered for its ability to do so
This deck died down over time, especially when Mox Opal was originally banned (Mox Opal is back, but there are plenty of stronger combo options in Modern than Cheerios)
The payoff you get just from this card alone is enough to make me think that youd strongly consider expanding into Grixis colors if you already have a demon tribal deck