Now that druids will be able to conjure SDs why not give other conjure ammo spell for sorcerers?
It could be a more expensive small explosive rune only conjured by sorcerers after finish holy rose or grim. The arrow and dmg sprite could be the same used by nightmares.
Small Explosive Runes on a 300 MS 1160 spellpower -> 170~400 dmg (40 runes for 960 mana)
Dark Small Explosive Runes on same lvl and spellpower -> 220~520 dmg (40 runes for 1440 mana)
50% more mana spent for 30% more dmg.
Numbers could be changed for balance purposes, just an idea.