This is a new monster. It appeared in your Inferno yard. It can be unlocked with a Strongbox.
Valgos is essentially a reusable Eye-ra, because Valgos targets walls, but doesn't blow up. However, because it doesn't blow up, it only targets one Block at a time. Therefore, it is useful to send a group of Valgos at a wall, instead of just one.
It is a good idea to send Valgos to a base where there are no standing Blocks, because Valgos's high damage can be used on other buildings.
Note: Stats are provided by World War 3.
It is one of the only two monsters that mainly targets walls.
It is the only burrowing Monster not related to Wormzer.