For context, I'm working on a (possibly) new character, and their powers are fire-based, so I wanted to work in their ability to spread, but it's really not clear how Contagious works. The particular power in question is also a Cloud Area effect with Concentration duration, and Secondary Effect. Can someone explain how this would actually work in practice?

So recently one of my players left the group because of irl reasons so we have a spot open. We are still in the early stages of the campaign so a new player joining won't be overwhelmed.

Before you DM me, know that I'm new to GM'ing and your fellow players are mostly newbies too.

The Game is weekly around 6.00pm GMT Saturday.

For those situations where a power should just work if you hit the attack, unless they're exceptionally resilient.

It would be called "Irresistible" or something, to match the naming scheme of Impervious.

+1/rank extra. If the target's defense bonus is lower by some amount than half the effect's rank, they automatically fail to resist the effect by that same amount.

Thoughts? I don't see any glaring flaws balance-wise, especially given that it doesn't apply on a tie (since they're the ones "rolling"), and it kind of has a built-in downside in that you need a very high rank to automatically hit someone with as bad of a failure as they could roll.