'Fortnite' teamed up with Marvel for a limited-time 'Avengers: Endgame' mode - here's what it's like to play

"Fortnite: Endgame" splits 40 players into two teams of 20, pitting the heroic Avengers against Thanos and his army of alien warriors.

To win, the heroes need to defeat the enemy team before Thanos can collect all six Infinity Stones, the mystic gems that control the Marvel Universe.

Unlike "Fortnite: Battle Royale," players can respawn when killed. The Avengers team will respawn an unlimited number of times, but if Thanos collects all of the Infinity Stones, their respawns will be deactivated.

Every player on the villain team starts out as a generic Chitari warrior, but the first person on the team to find an Infinity Stone will become Thanos.

Thanos has a range of attacks at his disposal, including a super-powered punch, a beam attack, and an extra-high jump that lets him crash back into the ground for massive damage. Chitauri invaders start with a laser rifle, a grenade attack, and a jetpack that lets them launch high into the air

If Thanos is defeated, another player on the Chitauri team will automatically transform into a fresh Thanos after a few seconds. Unlike the Avengers squad, the Chitauri team is limited to 100 respawns, which means about five respawns per player.

Players on the hero team will start with a treasure map that leads them to an Avengers-themed item.

When dropping into "Endgame," most of the usual "Battle Royale" mechanics still apply. You'll start with an assault rifle and shotgun on the Avengers team, but you'll want to find your special weapon right away.

Building is still available and your resources will automatically increase over time.

There are four items in total: Captain America's shield, Iron Man's repulsor gauntlets, Hawkeye's bow, and Thor's axe, called Stormbreaker.

The powers players get from the special Avengers items may not be as powerful as Thanos, but they're a ton of fun to use:

• Iron Man's repulsors let players fly through the air and shoot energy blasts
• Hawkeye's bow is equipped with grappling arrows for extra mobility and explosive arrows for damage
• Captain America's shield can block incoming damage and can be thrown at enemies like a boomerang
• Players can wield Thor's axe Stormbreaker as a melee weapon, fling it over long distances, or come launch themselves at enemies with a diving swing.

Thanos will grow more powerful as he collects the infinity stones, just like in the "Avengers" movies.

Whenever Thanos adds a stone to the his infinity gauntlet he gains powered-up abilities, and the other Chitauri gain health. Each infinity stone has a different effect:

• Reality Stone (Red): Doubles Thanos' heath and shields from 1,000 to 2,000
• Soul Stone (Orange): Thanos recovers shields when he defeats an enemy (called siphon effect)
• Mind Stone (Yellow): Thanos' jump height doubles
• Space Stone (Blue): Thanos' "ground pound" area of effect increases by 300%, and damage increases by 600%
• Time Stone (Green): A big knock-back is added to each hit, increasing by 300%
• Power Stone (Purple): Thanos' laser damage increases by 600%

The Infinity Stones appear at random locations around the map, and the storm from "Fortnite: Battle Royale" will shrink the play area over time.

"Endgame" will go on until Thanos gathers all the Infinity Stones and wipes out the Avengers, or the until the heroes kill Thanos and the Chitauri 100 times.

Chitauri invaders start with a laser rifle, a grenade attack, and a jetpack that lets them launch high into the air

"Fortnite" has also added a new Black Widow outfit.

The Black Widow outfit set includes the Widow's Pack as "back bling," the Widow's Bite Pickaxe, and Widow's Pirouette Emote. The Black Widow outfit costs 1,500 V-bucks in the in-game store, the equivalent of $15 cash.

Epic Games said the Black Widow outfit is one of two Avengers-themed sets coming to "Fortnite." The second will be released next week.

"Fortnite: Endgame" is a limited-time event, so there's only a short window for you to try it. The game is available for free on Android, iPhone, iOS, PC, PlayStation 4, Xbox One, and Nintendo Switch.