Raider armies spawn in 4 different difficulties: Super Easy, Easy, Normal, and Hard. Each one is eligible to spawn after obtaining iron, diamonds, blaze rods, and anchient debris respectively. Alternatively, the Ominous Battle Standard can be used to summon an army or increase the difficulty of an active army up to a secret impossible difficulty. Harder armies have the ability to spawn special raiders that drop informatioal accessories. Those raiders are The Warlord, Invoker (not evoker), Wizard, Giant, and Pterodactyl. 

The CRT TV is an informational accessory that isn't a port from Terraria. This accessory displays your FPS and can be obtained through the new Raider Armies. The battle standards are items that can be used to control Raider Armies. The Ominous Battle Standard can summon armies and increase the difficulty of active armies. The Warding Battle Standard can surrender to the active army, cancelling it.