What is the eternal puppetmaster? Well, it’s a chronurge. Unlike Ghost in the Machine, this particular tech only works with a chronurge. Particularly, we are a Dybbuk marilith chronurge. With this combo, We can essentially determine the outcome of most situations before they even happen.

We force every enemy save to be a fail, force all friendly saves to be a success. Force all of our ability checks to succeed, as well as force a friendly attack roll to hit. We throw out control spells, then force enemies to fail them

Dybbuk?

We’ve used this a few times already so this isn’t too surprising. The important part here is that Dybbuk’s are immune to exhaustion even while possessing other forms.

Marilith?

We true poly a simulacrum of ourselves into a marilith then nystuls it into a beast and possess it. why? for one particular trait

Reactive. The marilith can take one reaction on every turn in a combat.

usually this is good, but nothing spectacular, but on a chronurgist immune to exhaustion, we can use “Convergent future” on every turn.

Convergent future: You can peer through possible futures and magically pull one of them into events around you, ensuring a particular outcome. When you or a creature you can see within 60 feet of you makes an attack roll, an ability check, or a saving throw, you can use your reaction to ignore the die roll and decide whether the number rolled is the minimum needed to succeed or one less than that number (your choice).

When you use this feature, you gain one level of exhaustion. Only by finishing a long rest can you remove a level of exhaustion gained in this way.

Good thing we’re now immune to exhaustion.

What does this do

Well, we never fail saves and enemies always fail our saves, and we can always pass checks, and force enemies to fail checks. We can even force 1 attack a turn to miss or hit, as long as it’s happening within 60ft of us. We now exist as a chrono-aura, constantly re-writing events to go the way we want them to and not what the dice decide. This will not allow us to get past legendary resistances, but it will allow us to pass any save involving debilitating us, or 1 attack per turn against us. We can also force our allies attacks to hit, if we so desire.

This build is ultimately rather simple in how it works: convergent future on every turn, but it allows us to take near full control of the entire fight. We control the enemies turns, turning any chance of success they have into failure and any chance of our failure into success.