This can be challenging to understand for new players. To affect a being with magic resistance, all spell must penetrate, this also applies to Wards and the Aegis[1].
To keep a Might 30 being out with a Ward, you need to make a ward of 30th level that can penetrate the magic resistance of said being, in this case 30, so your casting total needs to be 60. The same would apply to the Aegis.
Many troupes play without requiring Wards and the Aegis needing to penetrate. Many troupes do. I find that requiring penetration can give characters (not necessarily the players) a reason to cooperate, at least once a year.
See, callen's Guide to Aegis of the Hearth.
So, in order to get a high level Aegis to penetrate, you need to come together with Wizard's Communion, and cast the spell. Also, Wizard's Communion has been corrected with the Muto Vim errata, and to affect a ritual spell like Aegis of the Hearth, Wizard's Communion must be of Sun Duration, taking 10 levels away from the power it can provide to the communion calculation.
Playing without penetrating Aegis & Wards is easier.
[1]This is controversial, some say that it is or isn't in the Rules As Written (RAW). My hope is that debate doesn't erupt here, but it is important for you to be informed now before a player asks, if his Ward needs to penetrate and then you need to retcon. Although retconning this can be relatively easy, too.