Redeemed can't cast or trigger offensive spells when at 0 MP.

[Repinuj]

Unnum can't cast offensive spells at pets (and presumably characters) when at 0 MP.

He noticed and decided to curb a Wraith infestation. When he dropped to 0 MP, he stopped being able to cast his attack spells at them. Neither from memory, nor from gems.

Probably related to them being listed as costing MP under the dropdown, even though they cost HP. Bow weapons still show up and can be used. Oddly enough, the gem of Greater Glyph Erasure also shows up, though he didn't waste a charge to test if it can be cast.

This refers to spells cast under 'Combat Actions'.

Utility spells cast under 'Spell Casting' still show up at 0 MP, correctly show as costing HP, and can be cast (at least Shadow Wrap). Only ones cast from memory, though. Gems still disappear under 0 MP.

EDIT:

Slight correction. Memory cast spells cast under 'Combat Actions' disappear from the drop-down when at 0 MP. Gems remain; it looks like somehow my remaining charged combat gems ended up turned off under 'weapons'. Don't recall ever turning them off, but I suppose it's most likely I turned them off accidentally at some point.

Under the 'Spell Casting' section for utility spells, it's the gems that disappear from the drop-down when at 0 MP. Memory cast spells still show up on the drop-down.

[Kandarin]

I think I've identified a cause and a solution.

[Repinuj]

Issue seems partially fixed. Memory cast attack spells no longer disappear from the drop-down under 'Combat Actions'.

Utility spell gems still disappear from the drop-down under 'Spell Casting' when at 0 MP. The whole drop-down disappears, actually.

All gems still read as costing MP under drop-downs, if they show. As do memory cast attack spells under 'Combat Actions'.

Memory cast utility spells under 'Spell Casting' correctly give the HP cost.