Making the Summon Spell
It's type should be Script, and it should be on Self. No conditions are necessary. You can make the visual effects whatever you like. Create a new script in the bottom right corner, and name it how you like it. Mine will be called TestFollowerSummonScript, and we're going to pretend I have a follower I want to summon named Benjy. You'll also need to create a new message (preferably messagebox) that will be shown when your follower is summoned. To do this, go to Miscellaneous>Messages, and create a new message (right click and select New). Then you'll need to fill your message property in the script, which looks like this:
Scriptname TestFollowerSummonScript Extends ActiveMagicEffect
Actor Property BenjyFollower Auto
;be sure to fill this property
Message Property SummonMessage Auto
;be sure to fill this property
Bool Ready = True
Event OnEffectStart(Actor akTarget, Actor akCaster)
If Ready; if we're ready
BenjyFollower.MoveTo(Game.GetPlayer(), 5, 0, 5, true)
Ready = False
Ready = True
Then we have an If check which makes sure that Ready is true. You can remove this if you don't want the spam-check. Once we've made sure it is, then we move Benjy to the player, with an offset of 5 units (x and z, since we don't want them to be floating we don't touch y) so he doesn't go inside of the player. Then, once he's been summoned properly, we show the message, change Ready to false so the spell can't be spammed for 3 seconds, and then change Ready to true again.
Now we need to attach our magic effect to a spell. So press OK and exit your magic effect, then go to Magic>Spells and create a new one. Name it whatever you like. You can make it's type whatever you like. I usually go with Lesser Power, but Spell or any other works fine. Make the effect the same one we just created by right clicking in the effects table and selecing Add/New and then choosing your effect from the dropdown in the effect's window. If you want any conditions on your spell, put them there, but mine won't have any. Now close your spell - and you're done! Go ahead and test it in-game.
Adding the Spell to the Game
On Game Start
We're going to create an alias for the player which will add the spell to the player as soon as they start or load a new game. So go to the Quest Aliases tab, then create a new Reference Alias (right click, new reference alias). Name it PlayerAlias, and ignore all the widgets, boxes, and other stuff. Click the circle next to Specific Reference, click the big rectangle that says Forced: NONE, and it should open up a new window. Where it says cell, choose (any) from the dropdown, and it should default to PlayerRef in the second dropdown. If it doesn't, find the Player in the second dropdown and click OK.
Now we add the script. Click Add in the scripts area in the right-hand side of the alias window, and create a new script. I'll call mine TestSummonSpellAddScript, though yours may be whatever you want. It should look something like this:
Scriptname TestSummonAddSpellScript extends ReferenceAlias
Spell Property SummonFollowerSpell Auto
Because otherwise, as soon as you start a new game, before you've even chosen your character, the spell will be added. Which, from my testing, doesn't actually work. Wait waits until you are no longer in a menu, and then Waits one second. This stops the rest of the code from running before it's supposed to.
Self.GetActorReference() will get the actor the script is on, in this case the player. AddSpell adds the spell within it's parameters, and false makes sure there's no notification like "Spell Added" in the upper left hand corner when the spell is added.
Once You Get Your Follower
Navigate to Items>Books, and create a new book. I actually recommend duplicating a currently existing spell tome, since then you don't have to choose all the texture paths and mesh paths. So I'll duplicate the spell tome for Conjure Familiar, and then right click and Edit my duplicate. You can change the ID to what you want, but for the name I recommend something along the lines of "Spell Tome: Summon Follower". In the area where the text is, replace the text with something simple like "Summon Follower". It's almost impossible to see the actual content of the book, but most spell tomes have the name of the spell written in them so I recommend it as well.
Choose your summon follower spell from the Teaches Spell dropdown, press OK, do NOT create a new form, and you're done.
What type of tutorial would you like to see next?