I think the effect on this card is fairly good, but I feel like 5 is a LITTLE too low for the amoutn of power it brings. I'd reccomend maybe bumping it up to 7, or at least 6.
I also think it is really good with the synergy of the deck so far, since you SHOULD have at least five zerg on the field easily, so I feel like this is one of those "Build the deck around the best card" type things, and this is like your trump card, and it shows in what it does. but like I said I would reccomend a cost bump :3 (preferably adding more than one red and other colorless, to make it a bit harder to summon. if you only bring it to six not seven, I would HIGHLY reccomend that six be a red)
please let me know if I'm being too harsh in any of these btw ^^;

so far no, but let me tell you why I feel he's already balanced and feel free to argue. He has 1 toughness. Any sneeze card can easily remove him. His presence as an intimidating creature is very easily nullified by how painfully easy he is to remove from the field

I suppose that is true. there are very many kill cards (I.E. lightning strike) that can take him out easily. so yea, I guess I can see it now. I suppose he is more of a glass canon type thing.
but even considering that, I still think even a one mana bump would be a debatable thing to add. I guess it would be one of those "you gotta playtest it to see how well/bad it does" type things. if it seems REALLY broken, up the mana, if not, dont. so yea I think this is a "experiment first" card XD
can't believe I didnt think of it that way XD

personally with what I've seen almost every deck (including mine) has some way to deal at least 1 damage to something

true XD my dash deck could do that easily

This is green, red, and black for 6.