Ace, known as "Spade" or "Fire Fist" in Universal Tower Defense, represents the pinnacle of Damage Over Time (DoT) strategy. Based on Portgas D. Ace from One Piece, this unit doesn't simply deal damage—he creates an environment where enemy survival becomes mathematically impossible through the "Burn Meta."

Unlike physical damage dealers who rely on kinetic impact, Ace functions as an elemental zoner. His attacks apply a persistent thermal condition to targets. Physical damage is an event; burn damage is a process. This distinction transforms Ace from a standard AoE attacker into a force multiplier who exploits burn mechanics to achieve damage outputs rivaling units of significantly higher rarity.

The Ace guide centers on understanding why burn damage outscales raw burst damage in high-level content. Most games use "Refresh Logic" where reapplying burn simply resets the timer. The Ace Burn Meta relies on breaking this through "Stack Logic."

The "Upgrade 2" Anomaly

The most critical insight is the "Upgrade 2 Anomaly." In almost every other unit, upgrading increases power. For Ace, upgrading past Level 2 increases raw impact damage but decreases Attack Speed (SPA rises from 3.53s to 4.22s). In a Stacking Burn build, Rate of Fire is the primary driver of DPS:

• Faster SPA: More stacks applied per minute
• Slower SPA: Fewer stacks, stacks fall off before critical mass

The disciplined player keeps Ace at Upgrade 2, saving money and maximizing thermal efficiency. Upgrading further can actually lower total damage output against high-HP bosses.

The Astral Trait Imperative

If Ace is the engine, the Astral trait is the fuel. Without it, the engine seizes; with it, it produces infinite torque. Astral (0.45% roll chance) provides:

• +30% DoT Damage (multiplicative boost)
• DoT Can Stack (the transformative mechanic)
• +20% Affliction Duration (more stack overlap)
• -15% Cooldowns (faster application)
• +20% Range (extended Time on Target)

Alternative traits like Ruler (damage), Sniper (range/crit), or Godly (speed/damage) fail because they lack the specific "DoT Can Stack" modifier. Without stacking, speed just refreshes the timer faster. Astral is the only trait unlocking S-Tier potential.

Strategic Deployment

Because burn damage takes time to kill, Ace is not a "Goalie" (last line of defense)—he's a "Midfielder." Place him at entry points of long straightaways or inside U-turns. Corner placement utilizing the +20% Range from Astral allows Ace to hit enemies as they approach, turn, and leave—tripling the stack application window.

Place Ace early in the track. You want enemies burning for their entire walk. If Ace is at the end, enemies die (or leak) before burn fully ticks, wasting potential damage.

Relic Optimization

The Master Ninja relic set is optimal, providing +120% Damage (60% each slot). Why raw damage? Because Astral already provides utility (Range, SPA, Duration). Astral only gives +30% damage; Master Ninja effectively doubles base burn. When this doubled burn starts stacking (2,200 → 4,400 → 6,600), boss kill time halves.