This is a general question mixed with possible bugs regarding the summoning of wildings and other things and their skills...

WildingShaman

<SelectedAbilityBonusOption>Spell_CoalStones</SelectedAbilityBonusOption>
<SelectedAbilityBonusOption>VulnerableToCold</SelectedAbilityBonusOption>
<SelectedAbilityBonusOption>Spell_Counterspell</SelectedAbilityBonusOption>
<SelectedAbilityBonusOption>Weak</SelectedAbilityBonusOption>
<SelectedAbilityBonusOption>Endurance1</SelectedAbilityBonusOption>
<SelectedAbilityBonusOption>SummonIgnys</SelectedAbilityBonusOption>
<SelectedAbilityBonusOption>Spell_SummonWilding</SelectedAbilityBonusOption>

I looked and this ability grants the SummonIgnys spell... my concerns

Do monster units have Mana? If not this unit will not actually ever summon a Ignys. Also, doesn't this ability give the creature the ability to summon Strategic spells (which is not intended I think for monster units) This could be an oversight as there is a mild internal name conflict (intended by the looks) with the ability SummonIgnys and the spell SummonIgnys

SummonIgnysFix

 I've provided a fix for the moment. It adds

The ability: Spell_SummonIgnys

The Spell: SummonIgnys_Ability

and a modified unit: WildingShaman

One can use this in the mods folder and all the effects should work as described.

On a second note the SummonWidling ability which summons the wildingriders appears to summon the unit on the ground and ignores the height of the mount when summoned. So you get a wilding half in the ground (the boar mount is underneath the ground). Maybe have the shaman summon a group of wilding warriors (3 warriors) instead.