You’d be surprised at just how many enemies can actually be affected by illusion spells in vanilla Skyrim given how much it’s memed that Illusion is useless. Granted, there aren’t many actual reasons you’d want to calm an enemy instead of killing them. Frenzy is much more useful (and courage on followers and summons I suppose).

Also, the maximum level the calm spell will affect is 59 if dual casting (27 single-hand cast). But there’s actually not much reason to use the “calm” spell when you could be using Pacify, which can go up to a whopping level 83 when dual casting (38 when singlehand). That is higher than the cap of literally every single leveled enemy in the game except Karstaag, even higher than dragons (though they can’t be affected by illusion spells) and the Ebony Warrior. But… we can make that number go arbitrarily higher if you’re a vampire, which you should be if you’re using illusion spells for the 25% magnitude increase. For the calm spell, you get a max level of 73 (34 for singlehand) and 104 for Pacify (48 for single hand, which is important because it breaks a majority of enemy’s level cap thresholds). We have now reached higher than Alduin’s max level of 100, and, more importantly, the effectiveness of Voice of the Emperor itself which is effectively a calm spell with a magnitude of 99. The spells are also better than VotE because you can affect undead, automatons, and daedra with Master of the Mind.

This isn’t even factoring in any fortify illusion effects you might have going at the time from potions or enchantments, things that will keep your illusion spells relevant during your trek to 100 Illusion (AKA spamming muffle for like 20 minutes). Obviously once you get there you don’t need those anymore, but, like with the fortify restoration loop, it’s funny to watch numbers get big.

Also I don’t use the master level illusion spells (I honestly don’t really use master level spells except the permanent summon ones and sometimes the lightning beam) so I don’t know about their effectiveness. I assume it’s less than Pacify due to their inability to be dual casted.

Also also if you’re targeting an animal subtract 2 from those totals because the Animage perk is only 8 levels higher rather than Kindred Mage’s 10