BlueSwann Although I'm not exactly sure of the timeline of events (so correct me if I'm wrong), after this Simon returns to Feroholm to support the chosen (which were early attempts by Hester to weaponize divine magic) and Riala started her explorations of the Tower. At this point Ivala intervenes by continuously spawning chosen for Simon while she points Riala to the shards. She keeps spawning chosen until Riala implants the shard in Simon, kicking off the entire story. This is supported by the fact that after Simon leaves chosen no longer appear in Feroholm.
riala at the start of the game is sixty, normal succubus lifespan is between thirty and forty. so she had fund the divine shard at least two decades ago, more probably three. roughly when wendis die. if this is a piece of ivala plan that plan should be older.
the chosen isa project of ivala captor, no doubt of that. xestris is very clear, and their nature is a big proof of that. can be a goddess inbued a lot of little shit with enough power without any mean to control the power or they behaviour? they are all "flawed vessel" (as the chosen targeting annah spoke of), can you think ivala can deliberatly choose flawed vessel if she can pick people how can put that power to real use and working for the good of the world?
During the story she intervenes several more times. The most obvious case is Carina, but also if I remember correctly the chosen that attacks the Incubus Emperor seems stronger than usual. In chapter 4 there is the little girl, also during the Erosian crisis a chosen appears to distract the Fucklord (although this could also be the work of Hester). Then in Chapter 5 it seems that Hester has perfected her control and that Ivala can no longer influence the world on her own.
the chosen are mere fooder, they don't need to do anything for real, thier existence is enough for the creator to collect data. in the light of the info xestirs give us tyhe chosen distract the fucklord was send to gauge the reaction of a (soul) sharholder to specific situation, thus growing their understand of the black shard (they had accesso only to a divine shard, so they need to study the other side of the equation)
BlueSwann Perhaps not since the founding of the church, but when Tertia is asked if Ivala founded the church the answer is unclear. I also got the impression from the conversation between Mitthyn and Ivala that she had been imprisoned for a very long time, since being imprisoned for less than a century is not a lot of time for Goddess. Also, the church used large scale holy spells during the Second Arclentian War, which points to her being enslaved quite a while before that.
tertia said ivala build her defense between the last cycle and the actual cycle (after the defeat of the "partial lustlord" enslaving mithyn, but before the actual generation of IKs rise). she is captive, but don't think in a 'physical' sense. after all mithyn was able to sneak past them for few moment to talk with her not long ago, even tanurak require some time to understand the protection of ivala. she is trapped in the tower by her decision, and the captor were able to build a system to cage her and harvest her power. like xerces had doing with zelica.
for the second arclentian war you are wrong, an old man in ardford during the 3AW said " Before it was a battle between man and monster, now huge spells are dominating the war..." and the iris' mage succubus advisor in regard of the ivala's wall "Holy magic, but... it's in a different class than anything I've ever seen before!" large scale spells were used, yes, but not tower-grade spells. the chosen project is new as well (wendis die before any chosen start to appear)