The world's in major danger in FoxNext's upcoming squad-based RPG Marvel Strike Force, thanks to the game's arch-villain, the infamous Kree warrior and Eternal, Ultimus, and his evil forces. It's up to you to collect a roster of at least 70 customizable and upgradable Marvel heroes and villains, such as Spider-Man, Doctor Strange, Groot, Rocket Raccoon, Loki, Elektra, Captain America, and Iron Man to defeat him. Before Marvel Strike Force goes live on the App Store and Google Play Store, Download.com got a glimpse of what you can expect from this much-anticipated game.

Launch Marvel Strike Force, and you'll learn the easy-to-grasp yet still engaging backstory. Ultimus, an Eternal whose power is only rivaled by Thanos, the Eternal-Deviant Hybrid supervillain from Avengers: Infinity War, is crossing dimensions and mind-controlling heroes, such as Spider-Man and The Incredible Hulk, to build an army to take over Earth. Working under Colonel Nick Fury, you control a counter-terrorist Special Mission Unit of S.H.I.E.L.D. (Strategic Homeland Intervention, Enforcement and Logistics Division) called STRIKE (Special Tactical Reserve for International Key Emergencies), so it's your task to recruit superheroes to defend Earth against Ultimus.

There are multiple modes to play in, including Campaign, four single-player story modes, where you fight for upgrades and new superheroes and villains; Events, which tells specific character stories and is the only place to unlock certain special characters; PvP Modes, where you battle it out in the Arena to become the best player in the world; and Alliance, where you and up to 24 of your friends can compete in ever-more-difficult raids for big rewards. If the single-player campaigns get your feet wet, introducing you to heroes, then villains, then the teaming-up process, and finally how to use cosmic characters to fight Ultimus, then the multiplayer and Alliance modes offer up the full breadth of the game.

The graphics are phenomenal, pushing your phone's hardware to the limit with impressive rendering, lighting, and visuals. This is especially evident in the more dynamic Ragdoll physics-based death scenes, where you can attack enemies and watch as they go flying to their doom.

Even complex moves are easy to perform in Marvel Strike Force. Three buttons on the bottom right of the screen determine your attack style. The first sets off a basic attack, the second, a special attack or assist, and the third, an ultimate ability, where you team up with others to do something spectacular. The hero you play is based on which character's blue indicator is full, and you select which enemy to take out with a tap.

Keep fighting successfully to fill up your heroes' energy reserve, and you'll be able to demonstrate special and ultimate skills. Pair specific heroes and villains to perform cool combo moves. The various chain combos, in particular, are astounding to behold and devastating for their target. For example, Rocket Raccoon can use Groot as a turret to fire his machine gun from and Yondu can fire his whistle-controlled Yaka Arrow, piercing everyone around him, who is not currently in stealth mode, by blowing into his tubular musical instrument. Fortunately the game pauses between every move, so you can pick it up and put it down when you need to.

Marvel Strike Force is free, and you don't have to spend a dime on in-app purchases. You'll start off with five players and then unlock more just by playing. You can amass close to a dozen characters just by playing for a week and reach Level 60 (or the final level) without spending money. Of course, you can still purchase in-game currency in order to buy new characters -- even superior cosmic characters -- for example, to speed up your progress for between 30 cents to just under $4. But you certainly don't have to.