Seismic Slam's radius is less than half of this. It is worth noting that this skill has the largest radius of effect for any skill for all characters. When maxed, this skill makes it that much easier to acquire Charge, with that 2 second stun inflicted on all enemies within 24 meters. Tremor has a very large range and decent knockback and is much better than Seismic Slam for that purpose. Since your skills aren't casted very fast, it becomes necessary to have a skill in your arsenal that allows you to escape a tight situation and find a safer location to fight. For instance, in co-op play, your Forcefield becomes invaluable to your party, so by having the monsters focus on other players, you can assist by gaining charge and casting Forcefield. This danger can be somewhat mitigated by Tremor, but still requires the player to think carefully in what situations to attempt to gain Charge. The inherent danger to this is, of course, that you actually have to be fairly close to an enemy to gain charge. At higher levels, when attacked by an enemy mob, your Charge will rapidly be filled. Forcefield receives a massive buff for each Charge acquired, therefore this skill is an absolute must to realize the potential of Forcefield. This is your only skill that gains Charge, and it does that well. Even near late-game, the amount of damage absorption by Forcefield is ridiculous. Even at level 1, this skill is still incredibly useful because any hit, regardless of how strong it is, will be blocked by Forcefield. The usefulness of this skill cannot be taken lightly. Your second most useful skill that will save you many a death, have this on right click as well. The reason why both Gun Bot and Sledgebot are needed is that having more minions means that less of the enemy is focused on you, allowing more freedom to run around and firing Blast Cannons and Dynamo Field. This skill doesn't need much explanation. Therefore, at a cooldown of 2.1 seconds, you will already achieve nearly maximum efficiency with this skill. Because of the setup time involved and the use in an actual boss fight, as long as the cooldown is sufficiently short enough to allow you to run and occasionally cast Spider Mines is enough. More points invested in this skill does not in any way increase the damage done, but decreases the cooldown time, and increases the summon duration, allowing one to summon more minions at any given time. Most people are under the misconception that it is necessary to max this skill. Combined with Spider Mines, which deals both fire and physical damage, your character is quickly able to bring bosses to their knees. The beauty of this skill is the secondary effect of increasing physical and fire damage taken by the enemy. This is your primary skill, always have it on right click. Near level 50, your character basically will not need potions anymore as this skill, combined with a strengthened Forcefield allows your HP and Mana to regenerate such that you can safely use skills with impunity. This skill is essential to this build and most engineer builds.

Torchlight 2 engineer build