Tunneler.The ankheg can burrow through solid rock at half its Burrow Speed and leaves a 10-foot-diameter tunnel in its wake.
Actions
Bite.Melee Attack Roll: +5 (with Advantage if the target is Grappled by the ankheg), reach 5 ft. Hit: 10 (2d6 + 3) Slashing damage plus 3 (1d6) Acid damage. If the target is a Large or smaller creature, it has the Grappled condition (escape DC 13).
Acid Spray (Recharge 6).Dexterity Saving Throw: DC 12, each creature in a 30-foot-long, 5-foot-wide Line. Failure: 14 (4d6) Acid damage. Success: Half damage.
Features
Powerful Bite — Passive: When a creature is hit by the ankheg’s Bite attack, it is considered Restrained and Vulnerable as long as the ankheg doesn’t move.
Acid Spray — Reaction: Countdown (Loop d4). When the ankheg is in the spotlight for the first time, activate the countdown. It ticks down when the ankheg is spotlighted or takes damage. When it triggers, creatures within Close range in a line from the ankheg are sprayed with acid and take 1d8+2 physical damage.
Tunneler — Passive: The ankheg can dig and move through the ground. It can move up to Very Close range through the ground per action spent tunneling.
Designer's note
The ankheg is a powerful low-level adversary that deserves a different version from the one already in Daggerheart, the acid burrower. It belongs in a hive of creatures working together to survive. It hunts, digs, and does all it can to protect its queen.
Why Bruiser?
The ankheg is an interesting monster because the Daggerheart SRD contains the acid burrower, a Solo version of the creature in Tier 1. Rather than duplicating it or just pointing you to what already exists, I made this a tough, formidable opponent that stops short of being a Solo, so it’s a Bruiser. This puts it above the average curve of the Adversary Stat Block Benchmarks in every way.
Keeping it unique
To set it apart from the acid burrower, I went back and forth to make sure it was a weaker variant and not too powerful. I looked at other Bruisers and compared them to Solos in their tier of play to follow as similar a curve as possible.
The fantasy
I imagine the acid burrower as the queen of a hive, with ankhegs as its soldiers. Since a Bruiser costs 4 Battle Points, 2–3 of these feels natural for an encounter; lean toward 2 if you want other adversaries as well.