Penultimate episodes are often tragic. They raise the stakes before the triumphant finale through making everyone miserable. Legends of Tomorrow will conclude its largely successful sixth season next week, but before then its ensemble must face yet another obstacle in this (relatively) more serious season – as serious a show with an intergalactic bowling tournament (where Planet Earth is one of the balls) can be.

“There Will Be Brood” mostly forgoes typical Legends hijinks for effective betrayals and heartbreaks, binding together the disparate season-long threads as it prepares for the endgame.

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Most immediate is Constantine (Matt Ryan) betraying the Legends through working with Bishop, his need for magical power outweighing his promise to start fresh with Zari (Tala Ashe). From the outside, the serious, cynical Constantine always looked like an odd addition to the goofy time-traveling Legends of Tomorrow, especially as the show pivoted away from the magic-themed 4th and 5th seasons, and Constantine cites this difference as never really having belonged to the Legends. He is unable to see what value Matt Ryan has brought to the show, who plays a hollow and opaque version of “classic Constantine” here, deliberately stiff in a way that reveals Constantine’s regression while he works with Bishop.

The two steal the Waverider from the Legends to search (again) for the Fountain of Imperium, while Astra (Olivia Swann) and Spooner (Lisseth Chavez) hide onboard. Since butting heads in “Stressed Western,” the two recent recruits to the Legends have forged a close friendship, while Astra is also keenly aware of how dangerous Constantine’s relapse is.

But when the Waverider lands, it unexpectedly pivots into Spooner’s backstory through stopping in 1920s Odessa Texas; Spooner’s hometown. There, miners are overworked by a greedy oil baron – “There Will Be Brood” referencing Paul Thomas Anderson’s There Will Be Blood – who threatens the Mexican healer Gloria for refusing to sell her land. Spooner instantly recognizes Gloria as her long-lost mother.

Spooner always assumed she and her mother were abducted by aliens. But the reality was that humans were responsible, the oilmen murdering Gloria on her front porch as a young Spooner ran away, stumbling into the extra-terrestrial Fountain that granted her powers and hid her away in the future. Constantine (leaving Bishop on the ship) helps Spooner fill in these gaps, claiming that in exchange for Spooner’s mystical Fountain-infused blood, this tragic past need never have happened.

But much of Legends of Tomorrow’s Season 6 has been how past mistakes cannot be easily scrubbed away, and that identity need not be so strictly fixed. Spooner’s decision to “save” her younger self – a plucky optimistic girl who likes reading War of the Worlds since space-aliens are not scary to her – would be at the expense of her current self, as she’d never go to the future, join the Legends or become friends with Astra. Spooner ruefully says how she’s a disappointment to her mum, but Gloria tearfully expresses how a brave, big-hearted time-traveler is much to be proud of. Spooner sticks behind to defend Gloria from the oilmen but allows Astra to take her younger self away to the Fountain.

This Fountain has become the epicenter of all the Legends story-arcs. As Constantine and Bishop stalk it out, it’s revealed to not just be an alien “gift” but an alien “being” in itself. Specifically, a giant extra-terrestrial mushroom that bestows its powers upon the worthy. Bishop whips up a serum to shift Constantine’s cells into those of an “innocent,” scientifically bypassing the magical morality test. Constantine is well aware Bishop wants the Fountain’s powers for himself, but perhaps arrogantly believes he will be one step ahead.

Meanwhile, the rest of the Legends are stuck back at Constantine’s house, without a Waverider or time-courier to follow him. But “There Will Be Brood” cleverly uses another plot thread to tie it together, Mick Rory (Dominic Purcell) and Kayla’s alien egg babies. Since she has a time-ship, the Legends conspire to get her attention, Gary (Adam Tsekhman) suggesting a fake social media “maternity” post of Mick posing with his eggs (a welcome bit of Legends levity in an otherwise intense episode).

This lets Zari’s “influencer” experience pay off, although Tala Ashe mostly plays her role with determined sincerity of stopping her boyfriend Constantine from doing anything (more) that he regrets. The social post works, and the Legends convince an annoyed Kayla to take them to the Waverider where the real eggs are. They find the ship fairly easily, but onboard Bishop has installed an automated bomb linked to the egg’s crib, which detonates in Mick’s face just as he hurried picks up the last few eggs.

That isn’t the only cliff-hanger of “There Will Be Brood.” Constantine and Bishop reveal the Fountain (thanks to Spooner’s blood) in its glorious full mushroom form. Although Legends does not treat this ridiculous entity as a joke, instead soaking in the quasi-angelic benevolence that it exudes. Constantine takes the serum to become part of it, but Bishop has spiked this with a deadly poison. Bishop didn’t want to join the Fountain but destroy it, which in turn would leave the Earth unprotected from his invading alien forces.

Poisoning the Fountain makes Spooner – who just successfully defended her mother from the oilmen - collapse, but Constantine’s own demise seems more certain (especially given the reports that Matt Ryan will return to Legends as another character). Astra and Zari find him just as he fades away and is mummified by the Fountain fungus.

Constantine suffered some setbacks these past few episodes, but his brief deathbed speech has enough time to express his regrets and his happiness at seeing Astra survive out of Hell. “There Will Be Brood” is a fairly solemn installment, but like how mushrooms grow in damp caves, Legends of Tomorrow must pass through this effective and heart-wrenching episode before the proper finale next week.

Legends of Tomorrow airs on Sundays on the CW.

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