what the miners cracked open
It does not breathe, and it does not tire, and every strike it takes only seems to close over.
Nobody in the Ore Wall crews agrees on which shaft they were digging when the wall stopped being wall. What's agreed on is that something came up out of it standing roughly the shape of a person, made of the mine's own bedrock, and it hasn't left the deep tunnels since.
Unlike everything else in this batch, the Rockheart isn't a corrupted person or a monster with a grudge - it's a real Huge Earth Elemental, built straight off the SRD numbers rather than grafted onto class levels. Its threat is entirely physical: it hits, it gets harder to kill the longer the fight runs, and once it's finally hurt enough, it turns the floor itself against you.
Feats
Skills
Its opening game - nothing subtle, just a huge hit on whoever's closest.
Every 4th round: one strike on the nearest enemy for 2d10+8 bludgeoning. A failed Fortitude save adds a knockdown and a 1-round stun on top.
No escalation yet - this is the same hit, over and over, for the whole first third of the fight. The threat only changes once it starts taking real damage.
Triggers once at 66% and then does nothing new every round after - it just keeps adding a little more damage reduction, round over round, capped at 8 stacks.
This is the one mechanic in the whole batch that's a pure passive escalation rather than an active ability - there's no roll to resist it and nothing to dodge. The only counter is DPS: burn it down before the DR stacks make that harder.
It keeps hitting with Tremor Slam on its usual timer the entire time Harden is stacking.
Roots itself in place for good and turns the ground under it into the weapon.
Every round from here: a bludgeoning tick (2d6) plus a movement slow to everyone within 4m, on top of its usual attacks. It gives up its own mobility entirely to do it.
A genuine zone-denial phase rather than another single-target hit - anyone who wants to finish it off has to be willing to stand in the grind.
This is the one boss in the batch built from a real published stat block rather than assembled from class levels - a Huge Earth Elemental is CR 7 in the 3.5 SRD outright, which made it the natural starting point for "deepest, oldest thing in the mine." The revision to CR 16 scales the same elemental proportionally up to 18 Hit Dice rather than changing its identity - Str 35 / Con 23 with a real earth elemental's frame still gets there without needing an inflated Con score, and the whole design is still that it gets harder to finish as the fight goes, not that it starts unkillable.
Harden was built specifically to be a mechanic type none of the other four use: a pure stacking passive with no save, no target selection, nothing to react to except the clock running out on your damage window. It's the counterpoint to Aldric's stances and Korrgath's forced movement - a boss that just quietly gets tougher to kill is its own kind of pressure. None of its DCs or damage dice changed in the CR revision.
| Var | Meaning | Value |
|---|---|---|
| BOSS | bypasses the drop-rate roll entirely | 1 |
| LOOPS | loot generation passes | 2 |
| CLEAR | inventory cleared before filling | 1 |
| TYPE | item category rolled | 26 (Boss Drop) |