I took a really good look at the rune stones and its worth sacrificing the higher level known that you lose out on in exchange for the power of the runes (you don't actually have to possess said master rune to use it, if you pick it as your rune discovery).
Take for example the Rune of Kalt, if your a Necromancer Wizard you can give not only yourself, your fellow party members, your mount an Icy Mantle that will reduce the first hit you take to zero, but you can grant your whole undead army an icy mantle as well.
Freezing Bolt isn't a spell, its more akin to a Paladin's Divine Smite feature, except it doesn't require a weapon attack. That means it doesn't suffer from the limations of spells, such as it would still effect creatures that are immune to spells or resistant (like an Empyrean's Magic Resistance), it can be used in the same round as a none cantrip spell (if say you cast a spell as a reaction for example), ect... it even does descent damage, with a nice effect. Oh and no Caster stat required which makes it great for Characters that have high physical stats instead.
Ice Brand basically allows you to turn 1 weapon or 20 pieces of ammunition into a magic weapon for 24 hours, one you don't have to wield yourself if you don't wish to. If the case of the ammo, you can give some of the ammo to multiple characters. This appears to stack with the normal bonuses of an enchanted weapon.
Winter's Howl basically gives you sleet storm as an encounter power (as close as 5e gets to encounter powers).
Frost Friend makes you resistant to Fire damage, that will help keep you alive against all the enemies that deal fire.
Frigid Touch seems like simply a cantrip until you realize that that 10 feet of frozen water has no duration (although I assume it would melt eventually on it own), and that you can use it an unlimited amount of times unlike a cantrip which can only have so many active uses in effect at a time. So you can use it to create an ice bridge to get across a lake, use it to build things out of ice, lock an aquatic enemey in a block of ice, make ice boulders for a catapult ect...
And that's just one Rune. Some one who prefers ranged combat might pick Vind instead for its awesome mix of mobility enhancement, ranged enhanced ranged weapons, and a the only ranged rune magic attack, which also pushes an enemy further way.
Or some who specializes in fire magic or a fire breathing dragonborn, or even a melee fighter or rogue who would like to boost they're damage out put, would get alot of use out of the Ild rune.
Stien is great for a Fighter or Paladin who wants act as a defender in the locking an enemy down (with the rune Kalt working great in conjuction to boost tankiness and Ice Bolts speed reduction).
You can create awesome builds around this, and thanks to discover rune, the character doesn't actually have to own the Rune to use it, unlike other characters.
I'll also note that the abilities that change damage type work in interesting ways with the Mysic's Immortal Order's Weapon Displine (I forget what its called).
