Universal Tower Defense X added the Merciless God Ultra Boss as part of the Universal Festival Part 2 update. This boss is classified as a Tier 4 Portal, making him one of the most challenging enemies in the game. He routinely applies status ailments upon your units, which can severely debilitate their ability to deal damage to the boss.
Here’s a complete overview of the Merciless God Ultra Boss in Universal Tower Defense X.
Breaking down Merciless God Ultra Boss in Universal Tower Defense X
Boss fight structure
The Merciless God Ultra Boss battle is a 15-wave stage, where you take on Divine Clones for the first 14 waves. You can access this boss battle using Merciless God Keys, which drop from the Otherworld Disturbance Legend stages.
The first 14 waves primarily function as the preparation phase, giving you time to perform upgrades and ensure your units are ready to take the boss down. Throughout the battle, Merciless God will attack units randomly, potentially stunning them.
Once you reach the 15th wave, Merciless God and Immortal God will appear on the battlefield, ready to take on in combat. At this point, your units should be at max upgrade level and ready to take on the boss. Merciless God has 2.5 million HP, while Immortal God has a health pool of 100 trillion instead. Target Merciless God and defeat him to move onto the second phase of the fight.
The second phase has you take on Merciless God (Divine), who has a health pool of 9 million. At this stage, Immortal God disappears from the battlefield; he will come into play later on. Reduce his HP to zero, and his health pool will immediately be refilled, while his max HP will be raised to 15 million. Doing so once more restores his HP again and double his max HP, giving him 30 million max HP.
Defeat Merciless God (Divine) once more to defeat him, causing Immortal God to spawn with 18 million HP. This will also cause a timer to appear on-screen, lasting 750 seconds or 12 minutes and 30 seconds. You must finish the battle within the specified time limit to avoid losing the battle.
Like his predecessor, reducing Immortal God’s health to zero will cause his HP bar to refill and raise his max health to 30 million. This process repeats until his max HP is at 60 million; defeating him at this point will begin the final countdown. Even if your countdown timer has hundreds of seconds left, the final countdown will cause it to jump to 15 seconds. Rush over to the button on the map that calls the Multiverse Creator to clear the boss battle and earn the associated rewards.
This guide explores Ultimate Fused Warrior, one of the best DPS units in Universal Tower Defense X.
Strategy and recommended units
The Merciless God boss can make use of the following actions:
- Divine Ball: Attacks and stuns a unit. Comes into effect before the boss fight begins.
- Divine Lightning: Attacks and stuns a unit during the boss wave.
- Sickle of Sorrow: Charges an attack and launches it after a while. Can be avoided by paying Ultimate Fused Warrior to stop him.
Considering how lethal Merciless God can be through his chain stuns, it’s important to use units that can avoid being stunned. Units like Merciless God (bottom path) and Evil Demon can ignore Stuns, with the latter having an ability dedicated to countering them.
Being in close proximity to Ultimate Fused Warrior NPC on the map once Wave 15 starts is also important. Sickle of Sorrow can potentially end your run prematurely, so preventing it as soon as possible is paramount to your success. Ultimate Fused Warrior’s position on the map is also relatively close to the Multiverse Creator button, so you won’t have to scour the map at the end of the battle.
If you are using a Synchro Drive unit like Fused Warrior (Super), be sure to perform the Synchro Drive well before the boss battle starts. Fused Warrior (Super), in particular, benefits from being on the field at least a minute before the boss spawns.
You can play the boss battle with friends if you’re feeling unsure about your units’ capability to defeat the boss. This will scale the boss’ HP higher based on the number of friends in your party, but other players’ help can be instrumental in your success.
Here’s a list of units that perform well in this Universal Tower Defense X Ultra Boss stage:
- Universal Merciless God
- Universal Joyful Captain
- Secret Ancient Shinobi
- Boundless The Strongest of Today
- Secret Pirate King (Voyage)
- Unrivaled Triple Threat
- Synchro Drive Fused Warrior (Super)
- Unrivaled Angel Born in Hell
- Secret Evil Demon (Rage)
- Secret The Drink (Super Rage)
Use any combination of these units with Bulmo and Fastcart on your team to attempt the boss battle and potentially walk away with a win.
Ultra Boss rewards and shop
The rewards you can potentially receive upon clearing the Merciless God Ultra Boss include, but are not limited to, the following:
- Fused Warrior unit
- Merciless God Keys
- Capsules
- Universal Gems Part 2
- Gems
- Universal Gems
- Trait Rerolls
Capsules are a new currency used to buy items at the Ultra Boss shop. Here’s a list of items purchasable at the shop:
- Stat Locks: 200 Capsules
- Sword of Hope: 1,500 Capsules
- Relic Rerolls: 200 Capsules
- Trait Rerolls: 100 Capsules
- Stat Rerolls: 150 Capsules
- Jacket of Fusion: 1,000 Capsules
- Spirit Sword: 1,500 Capsules
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FAQs on Universal Tower Defense X
When was the Merciless God Ultra Boss added to Universal Tower Defense X?
The Merciless God Ultra Boss was added to Universal Tower Defense X on June 2, 2026, with the Universal Festival Part 2 update.
How do I get the Fused Warrior unit in Universal Tower Defense X?
The Fused Warrior unit is available as a random drop from the Merciless God Ultra Boss in Universal Tower Defense X.
How do I stop Merciless God Ultra Boss’ Sickle of Sorrow in Universal Tower Defense X?
You can pay Ultimate Fused Warrior NPC on the map to interrupt the Merciless God Ultra Boss’ Sickle of Sorrow.
Edited by Swapnil Joshi
