I noticed that Ice Blast has a typo in its COREAbilities file. See below:

<AbilityBonus InternalName="IceBlastAbility">

<AbilityBonusOption InternalName = "IceBlastAbility">

<DisplayName>Ice Blast</DisplayName>

<Description>This unit is able blast an enemy unit with ice, causing them to lose their next turn and take 5 damage.</Description>

<Icon>IceBolt.png</Icon>

<GameModifier InternalName="DrowningStrike">

<ModType>Unit</ModType>

<Attribute>UnlockCombatAbility</Attribute>

<StrVal>IceBlast</StrVal>

</GameModifier>

</AbilityBonusOption>

</AbilityBonus>

It should say IceBlast but I think you pasted it and forgot to change the spell name. This would be a quick fix.