That's why I wanted to use the useskill command instead and trigger another direct summoning spell.
But seems I'm doing it wrong.
Any other restrictions to use that command?
Not 100% sure what you're trying to do here, but for the CharacterUseSkill script, here is an example from my mod Dunamis.
And just to make sure, you are trying to do this in charScript right? Because in the story editor there is no functionality for this AFAIK.
INIT
CHARACTER:__Me
EXTERN CHARACTER:%AttackTarget = null
EXTERN SKILL:%SkillToUse = null
BEHAVIOUR
REACTION SkillOnReaction, 1100
USAGE ALL
ACTIONS
CharacterUseSkill(%SkillToUse,CHARACTER:%AttackTarget)
SetPriority(SkillOnReaction,0)
EVENTS
EVENT AttackFort
ON
OnCharacterEvent(__Me,"KillHighway")
ACTIONS
CharacterAddSkill(%SkillToUse)
SetPriority(SkillOnReaction,1100)
So the trick is you have to have some sort of event trip the Behavior so the character will cast the skill. In my script above I run the character event "KillHighway" from the story editor. Also you have to actually add the skill to the character. So in the script here When the Character Event "KillHighway" happens to __Me, the skill gets added and then I set the priority of SkillOnReaction to 1100 which will make it run.
Then the Reaction itself actually uses the skill based on the parameters set in the sidebar (everything that = null) and the character will cast Poison dart at %Attacktarget. After that the priority gets set to 0 again so it doesn't keep repeating.
Now if you are actually trying to do this in combat, you'd want to script it a bit differently. You could copy one of the skill scripts like Skill_Summmon_EnemyAir and bolt on your skill information in it. CMB_GiantCrab would also be one to look at since they summon little baby crabs at the start of each combat. I'm not the greatest in the world with charscripts so you'd have to do some digging on those.
Or if you want to roll your own, One quick and dirty way to do this would be to have the script run based on turn, similar to the tutorial skeletons in Cyseal.
INIT
CHARACTER:__Me
EXTERN CHARACTER:%AttackTarget = null
EXTERN SKILL:%SkillToUse = null
INT:%CurrentRound = 0
BEHAVIOUR
REACTION InitialTurn,1000
USAGE COMBAT
CHECK "c1"
IsEqual(%CurrentRound,1)
ACTIONS
CharacterAddSkill(%SkillToUse)
CharacterUseSkill(%SkillToUse,CHARACTER:%AttackTarget)
Sleep(2)
CharacterEndTurn()
SetPriority("InitialTurn",0)
EVENTS
EVENT Round1
ON
OnTurn()
ACTIONS
Add(%CurrentRound,1)
SetPriority(InitialTurn,1000)
So here they would cast your spell on turn 1 and then go back to normal behavior.
Also one thing I'm not sure on is how summons work with "AttackTarget". So I just left it how I had it with PoisonDart, which is an attack spell of course so it functions differently. So you might have to play around with it a bit.