Spell horn is awesome... weapon.
It casting spell, giving up mana cost for one cast, then multicasting spell on every
Target
In moderate area
And this works fine not only with "evoker's claws"
(Wich looking horrifically effective and accurate; killing team mates is our profession now)
But with "too many glyphs" addon you can go crazy with filter "Not player"

Good weapon...
That looks like mass baff
This took really long time to charge
Just like preparation
For example:...
glide, one time heal
uh...
slowfall..?

There's lack of buffs
Almost nothing to improve by spell

Simple potion buffs are too boring and making potions some kind of useless

Let's think about it...
Some ideas wouldn't hurt

1)"Ward"
Absorption
This one existing even in game
But the main problems is possible spam
Still, there's guarantee way to prevent it
"Sickness"
Like "Summoner sickness" that prevent summon spell effect from working until the end of debuff.

Then there's only final questions
How much absorption it should give
And how much time it takes to cure "Abjuration sickness"...

2. Weapon enchant
   Something more offensive...
   Simply turn all weapon damage to penetrating true magic seems too much op, I guess.
   But here's could be something else...
   What about % armour penetration with turning all weapon damage into simple magic damage that not making it penetrate armour completely?
   To regulate armour penetration...
   15-30% maybe

And last here...
Should effect dispel if affected Changing weapon..?

P.S.
Beware
Spells "using main hand weapon as catalyst"
Adding almost any weapon's stat effect, including enchantments

3)Spell blade
"Hit release"
"Hit spell form"
A buff wich is "propagate" spell form actually
(Hope I spell it correctly)
Some kind of lesser "Mage sword"(I forgot how that sword from ars nouveau were named)

Effect lasts for a little while
And doing same thing without amplify: touch spell on next hit by weapon
+I think, effect should wear of when casted once
Or when weapon changed/hiden

4)Death ward
Wich could prevent final hit to minimum one heart (2hp; and I don't know if it would be useful to add config for this value; Maybe just for "last chance" mod)
And then wear of
with short "Abjuration sickness"

This glyph wouldn't make thread of undying less useful
As it gives last chance to save undying charge
So it would be even synergy

There's a variant that could save any early damage for a short while after it activates
But maybe then it should give "Abjuration sickness" on cast too

P.S.
"Abjuration sickness"...
Wait
Is that thing could nefr healing glyph spam..?

5)"Repulsion spell"
Just more defensive Variant of "spell blade"
Instead of activation on hit and dispel
It could activate more times (But not unlimited; variant: just like orbit, 3 times)

Something like true hit orbit spell form
But here's propagate variant
+damage taken needed
Wich is sacrifice for spell hit guarantee
++This could be buff to friends of yours

etc
Everything - just ideas

And I hope you'll find it inspirational