Generally the Mountain Vargath are a slow but hard to stop force … except when they decide it’s time to be fast thanks to Ramming Advance. This event gives the faction some of its strongest starts against factions that want time. Often rushing the game next to the opponent, skipping the pushing part of the game into the trading blows which is something Mountain Vargath always want to do.
Other than skipping the push, if the push is already done, it can allow the Mountain Vargath to have some assassination potential, especially combined with Slagborn Fighters.
Finally, Ramming Advance is your ticket back into action after you play Stronghold. So this is a common one-two punch of hitting, Stronghold, and then coming right back in with a Ramming Advance.
However, in games where the action is focused on the middle of the field or your push in the front lines is already established, it is generally better to discard this for magic if it doesn’t seem the opponent will open his summoner for potential assassination.
To take advantage of this event you don’t need to wait for a perfect turn where you get to charge with 3 units, often just being able to charge with a single unit like a fighter that pushes the opponent summoner for other units to hit, may be enough to get value. But if you need magic, this is an event that may be too situational to find its time.