System mechanic

Apex Hunter and Terror Hunter

Opened with [U] · a kill tracker covering all 109 regions in the game

Every named region has one signature creature — almost certainly the same one shown as that region's "Boss" on this wiki's own region pages, since both describe the strongest thing in that region's spawn table. Setting foot in a region only counts toward the separate world-survey system; actually felling its signature creature is its own, harder hunt, tracked here.

Apex Hunter

Tracks your kills against all 109 regions' signature creatures, with escalating cash bounties as your count climbs — paid out at 10, 25, 40, 55, and all 69 (the target when this first shipped — see Version History for how it grew to 109), plus a completion badge for finishing the full set.

Terror Hunter

A companion tracker covering 12 mega-terror and endgame-terror creatures — deliberately excluding scripted one-off bosses, so this is a genuinely separate roster from Apex Hunter's region signatures. Its own milestone bounties scale much higher (5,000 to 50,000) to match how much tougher these fights are. Neither this panel nor anywhere else in the game states which twelve creatures actually count — see The Mega-Terrors for the full roster and what unlocks each one.

Full Completionist

A purely cosmetic badge awarded for holding both Apex Hunter and Terror Hunter completion at once. It pays nothing extra on its own — both underlying achievements already paid out individually — it's a title, not a second reward for the same work.

Version history

Apex Hunter added, covering 69 named regions at launch, with its own panel opened by [U] and bounties at 10/25/40/55/69 kills.
Terror Hunter added the very next version, as the described companion tracker.
The Full Completionist badge added the version after that.
A 40-region hole closed, much later: 40 regions across two different eras of content had been explorable the whole time but had no signature creature assigned at all — they silently fell back to generic wilderness spawns and could never count toward Apex Hunter progress no matter how long you hunted there. Fixed by adding 40 new enemy types with proper region assignments, taking Apex Hunter's real coverage from 69 of 109 regions to the full 109 of 109 the panel had claimed to track the whole time.
Fixed the target being unreachable by anyone, at all, ever. Three of those 109 signature creatures — assigned to the sea, the ocean, and the river — had never actually been placed anywhere in the world; each existed only in the text describing it and in the master list of apex creatures, with nothing in between that ever spawned one. That silently capped every player at 106 of 109 forever, taking the full completion bounty and the Full Completionist title out of reach for anyone, no matter how thoroughly they hunted. Fixed by making them actually spawn in their own waters, at a lower rate than other regions' signature creatures — nothing else about those waters, or any other region, changed, and the target stayed the full 109. Nobody was handed a free kill; the hunt just became genuinely completable for the first time. That fix turned out to address only three cases of a much broader miss — see below.
Fifteen more regions closed the same way, later still. It turned out every one of the game's nineteen "biome roster" regions had the identical problem the sea/ocean/river fix solved: standing in a region's own terrain and hunting for that region's own signature creature was quietly guaranteed to fail, because none of the nineteen biome spawn tables actually contained their own region's apex creature. The water fix above had only ever closed three of those nineteen. Fifteen more were fixed the same way in one later pass — reading straight from the shared apex-creature table rather than copying it, so a future rename can't cause two copies to drift apart — leaving exactly one of the nineteen (a late-game region with no apex creature ever defined for it in the first place, so there was nothing to fix) as the sole remaining exception.

Trivia

If you were capped at 106/109 for a long stretch of the game's history and gave up on Full Completionist as unwinnable, it's been genuinely possible since the fix above — worth another look.