1.) Transmute Rock to Mud

Looks like not difficult to implement (thinking of a lower lvl arcane version of earthquake)
AoE slow, minus AC/attack, bludgeon dmg (reflex save for half)

And MOST important of all, fills the gap of Transmutation AoE spell (partly CC and nuke in some way), and works on all kinds of non-flying mobs

I always liked the idea of being a high DC Transmutator (?). Disintegrate for dmg, Flesh 2 stone (living only) for single target CC, but sadly there is no AoE of any.

2) Similarly, the counterpart spell,
Transmute Mud to Rock
Reflex save, or permanent (long duration hold). It requires 2 spells and 2 saves after all.

3) And just a side note, the spell stone to flesh is actually able to turn a stone golem to a flesh golem. Not really important in DDO in any sense. Just think it'd be awesome if that's working.