RPGMemes

L15 scenario. The above are two entirely separate scenarios -- I was not assuming two chronomancers in the same party.

Let's simplify this from an action economy perspective so we aren't running into the reaction limits. Let's assuming combat lasts four rounds, and on each of the first three rounds, you cast Polymorph (killer whale), and use your Chronal Shift to force a reroll if they save, generally with the goal of burning legendary resistances. Obviously this works better with a bigger party casting save or suck, to burn them faster (you can only Chronal Shift once per round though) or you can use the L10 trick above if well prepared. Great, in the fourth round, you cast Polymorph (killer whale) again and force them to fail the save as a reaction. Take one point of exhaustion. Easy enough, right?

Well, magic jar is fun, but requires serious prep to reduce the risks. An L15 wizard should already have a lair where they can leave their body safely, and they'd need to capture their target and bring them to their lair. This is why I chose L15 for this scenario instead of L14, because you need access to the spell. Assuming your wizard has a Researcher background or something (so you can handwave the meta), you can use locate person to find a CR12 Duergar Despot who has immunity to exhaustion. They exist in Forgotten Realms at least. Your DM might rule they don't exist, and then you'll have a harder time finding a humanoid immune to exhaustion to capture to magic jar into. That whole capture scenario would be an amazing multi-session mini-arc.

So worst case scenario, the DM says such a target doesn't exist. Well, then you have to wait until L17 to pull this shit off. True Polymorph can create a humanoid that is immune to exhaustion (there are dozens of them!) to create a magic jar target. Or you can use Wish (also broken) to summon such a creature, or simply wish yourself immune to exhaustion.

I mean, if you're an L17 wizard, you're basically god anyway. But the Chronomancer can pull off godhood at L15 if they can become immune to exhaustion with magic jar.

Even at L14, with the exhaustion penalty, it's stupidly strong.

Side note: killer whale is my go to. It's huge, thus hard to carry away by minions; has a huge bag of hitpoints, hard for minions to slap once to return back to BBEG form; and has a speed of zero on land. A good BBEG will have contingencied dimension door or something, so it isn't foolproof. You can try to trap them in Mordenkainens Magnificent Mansion or something that prevents escape through teleportation, but that adds another layer.

Did I mention that wizards are broken?