Some ideas
Earth rune
summon some earth (just a base rune like fire, ice and lightning)
Copy rune
can be two things:
copies the rune behind it in a cast (if none copied then counts as nothing or maybe projectile rune)
clones an enemy you cast it on (obviously turning it friendly) and use all other runes as buffs depending on runes cast onto the enemy
Switch rune
allows you to switch with an object or enemy and all other runes used will activate on the switched object or enemy
Box rune
summons a box and multiple box rune makes it bigger. as for other runes used they will activate after the box is broken
Shadow rune
summons a shadow that behaves as a friendly enemy and will use any other runes you used in the cast once after cast (example: fire rune + shadow rune will make the shadow use a fire rune once then only be able to use basic attacks)
Blind (or confuse) rune
makes an enemy confused or blinded and they will move randomly attacking anything they bump into for a certain amount of turns (depending on how many of the rune you used)
Mask (or buff) rune
makes you buffed and any other runes added will make your basic attack have that element applied
Dimension rune
makes a basic attack around you in either 4 or 2 different directions
Upgrades
Bounce rune upgrade
when bouncing prefer enemies over objects
Leap rune upgrade
can leap over obstacles
New enemy: Gargoyle
Is a statue until you are right next to it and then attacks (it's not obvious that it's a statue it looks like any other object)
Maybe this can help you make the game bigger :)