While Dota Underlords has continued to receive patches over the past few months, they weren't exactly massive in size, or all that exciting to mess around with. The reason for this, as Valve has announced recently, is because all of their efforts have been going towards the release version and its accompanying "Big Update."
There is still no release date for the Big Update, but according to the most recent preview, it will be here in the very near future! So in order to help pass the time, as well as showcase what the update itself will bring, Valve has now released the first in a series of previews.
This one is mostly focused on two newly created alliances, as well as four of the upcoming heroes. The first new hero is Dazzle with his Shadow Weave ability that heals allies and damage enemies. As you might expect from that alone, he will be a part of the Healer alliance that greatly increases the effectiveness of all friendly healing.
The Insect alliance is the second and final one revealed today, and its passive effect is to spawn a swarm of spiderlings from the edges of the map that poison enemies and cause them to occasionally miss their attacks. Besides good ol' Sand King, three of the new heroes will make up this alliance: Weaver with his Shukuchi ability that lets him become untargetable and phase through enemies while dealing damage; Nyx Assassin with both Spiked Carapace that reflects damage and Vendetta that allows him to deal massive damage to enemies after teleporting; as well as Broodmother with her Spin Web ability that makes enemies lose attack speed, movement speed and cast speed.
While the details are still lacking, you can learn a tiny bit more about these heroes over at the official website. As for the rest, I'm afraid you'll have to wait until tomorrow for Part 2 of the Big Update preview to go live.