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Channel Source

If you're trying this mod with Divinity Unleashed, do the following:
combine a channelSource mod skillbook with an Identifying Glass, then enable the second option.

So is there a way to get more than one copy of the final channel source book in Act 3?

it's worded as a reward, but it seems to me like it's only a reward for one person. No one else gets to use it -- the book is consumed on use. Thoughts?

If you have the Script-Extender you can enable the debug-console and use console commands to get a copy of all the books. !S7_ChannelSource AddSkillbooks .

You can enable the debug-console by using LL's ModManager or manually by creating https://github.com/Norbyte/ositools#configuration in the bin folder (Divinity Original Sin 2\DefEd\bin) with { CreateConsole: true }

Once in game, focus the debug-console and double-press the Enter key. This will put you in REPL mode. Type the console commands and all skillbooks should be added to your inventory.

I'm not sure I understand ...
The siphon source skillbook is in Meistr Siva's home in Driftwood.
If you're in Act 3 or beyond, you can use the ModMenu to get it.

The most consistent way to regen source in-combat in vanilla is consuming source-orbs, which serves as the balance point.
Consuming source-orbs has an AP to SP conversion factor of 1.0. They are pricey but gold is never a problem after act 1. If you have Five-Star-Diner then you get 2SP from 1AP! (cf. of 2).
Source-Vampirism has a cf. of 1 but is short ranged and requires corpses or enemies without magic armour.

Channel Source skills have cfs of 0.5, 0.67, 0.75

Each of these skills require you to commit APs, which are the most important resource in combat. It takes 8AP to regen and cast a 3SP skill. Assuming you topped-off before combat, this is at least round 3. Combat lasts 2-3 rounds on average.

Remember that regenerating source by itself does absolutely nothing and only wastes AP. You have to use that SP in the same fight to get the desired payoff. This means having a source-skill off cooldown and available to actually use.

Maybe you could increase the cooldown so it would be "more" balanced(?), 1 SP 1 CD, 2 SP 2 CD, 3 SP 3 CD, or something like that.

Time Warp requires 2AP and 1SP to cast. To get the needed SP using these spells you'll need to spend at least 2 more AP. Which adds up to 4AP.
Time Warp, under normal circumstances and for a regular character, provides one extra turn (i.e. 4 AP). That evens out to 0AP. You trade 1 turn of setup for 1 turn of Time Warp.

You can make this combo work depending on your party, other spells, tea, and talents like GC/LW. But on its own, I think it balances out.

Won't this spell become imbalanced in pair with "Time Warp" spell?

Like the rest, its hand-placed into the game-world and doesn't drop as loot. It should be at the end of the hall (Arena of the One) where that fight takes place. Might need to teleport to the raised platform.

Maybe im blind but i defeated the enemy needed to get the 5th skill and it wasn't on his corpse.