TL;DR
Demon Form is the engine, Limit Break is the payoff, and Major Update #2 left every core Strength card alone. The one change that matters is the finish line: Act 3 now ends against Aeonglass, a boss that rewards fast scaling damage and punishes block-and-stall. That plays straight into the item:ironclad's hands. item:demon-form races Aeonglass before its damage escalates, and the Ironclad's Exhaust effects clear the Wither cards the boss forces into your deck. Pivot when you see Demon Form in Act 1, ramp with item:inflame, and convert accumulated Strength through Sword Boomerang and Heavy Blade.
The Strength Build
The Ironclad's Strength build does one thing with rare efficiency: it turns the Strength buff into a damage multiplier that scales with how many hits you land per turn. Every point of Strength adds +1 damage to every attack. A 3-hit card at 6 Strength deals 18 extra damage. A card that fires four times at 6 Strength adds 24 damage on that single turn.
The engine is Demon Form. The payoff is Limit Break. Everything else in the deck exists to survive long enough to play them, draw them on schedule, or convert stacked Strength into a kill.
Through Major Update #2, the core Strength cards stayed untouched. Demon Form, Limit Break, Inflame, and Heavy Blade all carry the same numbers they did two updates ago. The standard Strength build was never the Hellraiser infinite that got closed in v0.100.0, so it survived that pass and every balance change since. This archetype holds the highest damage ceiling in the Ironclad's kit and one of the highest in the game. You trade early tempo for late-fight dominance. Demon Form costs 3 energy with no immediate return, and the turns that follow pay it back in full.
item:burning-blood, the Ironclad's starter relic, heals 6 HP at the end of every combat. That is not a side note. It is what makes the build viable. You accept HP trades in early rounds to hold energy for powers, and Burning Blood covers the interest.
Build: b5fe26a061fbWhen to Pivot Into Strength
The build wants an early commit, but not on Act 1 card one. Pivot when a reward screen gives you a clear signal.
Demon Form offered in Act 1. This is the primary indicator. Take it regardless of what else sits in the reward. The deck reorganizes around it.
Limit Break offered in Act 1. item:limit-break alone is not a reason to pivot, since it multiplies Strength rather than generating it. Seeing it early tells you the Strength archetype is seeded in this run's pool. Keep picking Strength sources and Limit Break pays off in Act 2.
Inflame offered. A single Inflame is not build-defining, but two Inflames with nothing better in the pool is a soft signal. You are generating Strength without Demon Form. Plan to find Demon Form in Act 2 and bridge with Inflame until then.
Two or more multi-hit attacks in your first reward screens. Sword Boomerang plus a second multi-hit card early means your pool leans that way. Strength converts multi-hit attacks into burst damage. If the hits are there, commit to the scaling.
If none of these appear, stay flexible. Take block, take removal, take Vulnerable application. The pivot only makes sense when the engine card is in reach. The Ironclad card tier list ranks every pick so you can read a reward screen at a glance.
Core Cards
Demon Form is the engine. 3 energy, Power, Rare. Base Demon Form gives +2 Strength at the start of every turn for the rest of combat; the upgraded copy, Demon Form+, gives +3. You play it, lose your offensive turn, and gain Strength before drawing on every turn after. With an upgraded copy running for three turns past cast, you sit at +9 Strength applied to every attack. Across a long boss fight that compounds into a number nothing else in the game reaches over a single combat.
Limit Break is the payoff. 1 energy, Skill, Rare. It doubles your current Strength, then exhausts; the upgraded copy keeps itself in the deck instead of exhausting. Use it after Demon Form has run for two or three turns. At 9 accumulated Strength, Limit Break makes 18. That 18 applies to every hit of every attack for the rest of the fight. One use closes most Act 3 bosses.
Inflame is your early ramp. 1 energy, Power, Uncommon. It gives +2 Strength on play (+3 upgraded), permanent for that combat. Before Demon Form lands in Act 1 and early Act 2, Inflame is the difference between your Strikes hitting for 7 and hitting for 9. Stack two if offered.
Sword Boomerang is your most energy-efficient Strength dump. 1 energy, Attack, Common. It hits three random targets for 3 damage each (four hits upgraded), and Strength applies to every hit. At 6 Strength each hit deals 9, so a single energy buys 27 damage. Against a lone boss all three hits land on the same target. This is the cleanest conversion of Strength into damage in the deck.
Whirlwind is the multi-enemy finisher. X energy, Attack, Uncommon. It spends all your remaining energy and hits every enemy once per energy spent for 5 base damage (8 when upgraded), with full Strength added to each hit. At 3 energy and 10 Strength that is three hits of 15 per enemy, 45 to each target in the room. The more energy and Strength you bring, the harder it scales, which makes it the build's answer to a crowded room.
Heavy Blade is the single-target spike. 2 energy, Attack, Uncommon. It deals 14 base damage and applies Strength at triple rate (five times on the upgraded copy). At 8 Strength, base Heavy Blade swings for 14 + 24 = 38 from one card; upgraded, the same Strength feeds in at five times and the number climbs higher still. Dead weight before Strength is set up, a one-shot tool once it is.
Relic Priorities
Ice Cream (Rare) carries unused energy into the next turn. This relic turns the Demon Form turn from a full offensive sacrifice into a partial one. The bigger swing comes on Limit Break turns: carry two stored energy into a turn where you play Limit Break for 1 and pour the rest into a full Whirlwind.
Paper Phrog (Uncommon) pushes Vulnerable from a 50% damage bonus up to 75% on the affected enemy. Bash applies 2 Vulnerable for 2 energy. With item:paper-phrog, any attack that follows item:bash lands 75% harder. At 10 Strength a full Sword Boomerang reads 27, and the bonus pushes that to 47 for a single energy. Bash plus Paper Phrog is worth roughly 20 extra damage per attack turn against a Vulnerable target.
Pantograph (Uncommon) heals 25 HP when you enter a boss fight. The Strength build accepts HP trades through Acts 1 and 2 to keep energy free for powers, and item:pantograph refunds most of that cost right before the fight where HP matters most. Pair it with Burning Blood and your HP line through the first two acts is far flatter than it looks mid-run. The Act 3 boss relic guide covers which boss relics keep the Strength plan intact.
Burning Blood (starter) heals 6 HP after every combat. You do not pick this one; it starts with you. It is the reason the build can take HP risks other archetypes cannot. Every fight you spend 10 HP to hold energy and cast Demon Form on schedule, Burning Blood hands 6 of it back. Over a full run that is 60-plus HP returned for free.
Act-by-Act Gameplay
Act 1: Gather Strength Powers
Act 1 is not about big damage. It is about installing the engine and building a survival shell around it.
Take Demon Form or Limit Break when offered. Take Inflame when offered. Without Strength powers, take Vulnerable application through Thunderclap and Bash, block cards, and one or two multi-hit attacks. Sword Boomerang is the best early multi-hit pickup.
Do not pad the deck with low-value Attacks. The Inflation modifier at Ascension 6 raises card removal costs, so every weak card you add in Act 1 sticks with you. Five Strikes, four Defends, Bash, plus four to six strong picks is a tighter deck than one bloated with twelve additions.
The Act 1 boss usually falls to straightforward play: Bash into heavy attacks, block when you need to. You do not need Demon Form running to win here. You need Demon Form in your deck.
Act 2: Start Dumping
By Act 2 you should hold Demon Form, one or two Strength sources, and three or more multi-hit attacks. The plan shifts from survival to acceleration.
Play Demon Form on turn one of every elite and boss fight. Accept the tempo loss. From turn two on, your attacks outpace any Strength-free deck. Act 2 elites carry 60 to 120 HP; with Demon Form running for two turns and a Sword Boomerang or Whirlwind to cash in, they fall in three or four turns.
Pick up Limit Break in Act 2 rewards if Act 1 did not offer it. It is your finisher and Act 3 demands it. Shops are worth a look here if the gold is there and Limit Break is on the shelf. Ice Cream and Paper Phrog show up in Act 2 relic pools, and both earn a skip on a neutral relic.
Act 3: Racing Aeonglass
Act 3 ends against Aeonglass, and the matchup suits the Strength build better than the old finish did. Aeonglass opens with roughly 512 HP (535 on Ascension 8) and 3 stacks of Artifact, and it carries Withering Presence: every 6 cards you play, it adds a Wither to your hand. Wither is an unplayable colorless status card. Leave one in your hand at end of turn and it deals 3 damage to you, 6 if the boss has upgraded it. Its Increasing Intensity move shuffles more Wither into your deck, hands itself 3 Strength, and sharpens the Withers already in play, so the longer the fight runs the worse it gets.
That escalation is exactly what Strength beats. The build does not stall and grind; it stacks Demon Form, doubles with Limit Break, and ends the fight before Aeonglass's damage climbs out of reach past roughly turn 10 to 12. The Ironclad also answers the Wither problem directly: Exhaust effects clear those unplayable status cards out of your hand and deck before they punish you.
The kill plan stays familiar. Turn one, play Demon Form and block what you can. Across the next few turns let Strength stack, then fire Limit Break once you sit at 6 or more Strength. The turn after Limit Break, every hit lands with a heavy bonus. A full Whirlwind, a Sword Boomerang, and Heavy Blade together carve through 512 HP in a single payoff window. The one wrinkle: those 3 Artifact stacks eat your first three debuff applications, so Bash and Thunderclap Vulnerable get absorbed until you have spent through the Artifact. Plan the Limit Break turn without leaning on the Vulnerable multiplier unless you have already broken the count.
Counters
Multi-hit-immune enemies strip the build of its best damage converters. Sword Boomerang, Twin Strike, and Whirlwind all underperform against targets that cap hit count or cut multi-hit damage. Read intent icons early. Against single-hit-only enemies, shift to Heavy Blade and item:bludgeon (3 cost, 32 damage, 42 upgraded) as your damage cards.
Weak debuffers cut attack damage by 25%. Weak does not touch Strength directly; it shaves the total after the multiplier resolves, so 15 bonus damage drops toward 11. It softens the build rather than stopping it. Outpace it with Limit Break and clear it where you can.
Artifact stacks block debuff application, and this is no longer a generic aside. Aeonglass opens with 3 Artifact, so the first three Vulnerable applications from Bash and Thunderclap get eaten before any stick. Against any Artifact carrier, plan your Limit Break turn around raw Strength rather than a Vulnerable bonus until you have broken through the count.