Warning! The following contains spoilers for the upcoming "Crisis On Infinite Earths" crossover on The CW. Read at your own risk!
Batwoman just aired its final episode before the start of the "Crisis On Infinite Earths" crossover, and of course, there was a tease to the big event. Oddly enough, the tease itself was not connected to Batwoman at all, but rather cut away to a character that had been featured prominently on The Flash. We can tell you what happened with Nash Wells during his appearance on Batwoman, though it's unclear exactly what his big scene prior to Crisis means.
After the dramatic conclusion to the Batwoman action in the episode, the scene cut to Central City. Nash Wells was seen in the city sewers standing in front of the Eternium door that allegedly housed The Monitor. Nash Wells revealed he had waited many years and traveled a long distance to kill Monitor, but now that the moment had arrived, he couldn't. In his words, The Monitor saved his life, and it seemed that was enough for Nash Wells to spare the powerful being.
Once the two put that behind them, Monitor asked Nash Wells to submit. Wells approached the door, and hit the symbols in a specific sequence. There was a brief pause, but soon after the sewer was filled with a golden light that eventually sucked the adventurer into the space behind the door.
What happened to Nash Wells? We don't know for sure, though we can speculate. Wells "submitted" to The Monitor, so it's likely he will be seen again during "Crisis On Infinite Earths" as an agent of The Monitor. Nash Wells may come out of that golden light as an entirely different person, but who?
Although we can't be certain, my guess is that Nash Wells will become Pariah. In the comic book "Crisis On Infinite Earths," Pariah was saved from Anti-Monitor by The Monitor, which may explain Nash Wells' whole little speech. While Pariah is more or less invulnerable and immortal, he's physically powerless to the events that pass. Admittedly, Nash Wells could become someone else in the mega crossover, but this theory seems to check a lot of boxes especially considering Pariah is confirmed to appear.
Other possibilities could make Nash Wells another character in the crossover, even if it's not exactly clear who else he could be. It's also possible Nash Wells was fooled into pursuing the Anti-Monitor, or lied about who he was seeking out to Team Flash. That would be a great way to introduce the presently unseen villain of "Crisis On Infinite Earths," if somewhat unlikely.
Got an idea on what's next for Nash Wells? Drop an idea in the comments below and be sure to tune in for the beginning of "Crisis On Infinite Earths" on The CW Sunday, December 8 at 8:00 p.m. ET. Stick with CinemaBlend in the meantime for more details on the Arrow-verse, and for more events in the world of television and movies.