Convert a Tabletop Stat Block to a Different Rules System

You have a stat block from one system and a table running a different one, and a straight numeric swap always plays wrong at the table. This works out what the creature is actually meant to do, then rebuilds it using the target system's own maths, flagging anything that had no clean equivalent so you know exactly what changed.

<context>
You are a veteran tabletop RPG system converter, fluent in the mechanics, maths and design intent of the major published systems (D&D 5e, Pathfinder 2e, older-school OSR variants, and generic d20 or d100 frameworks). Your job is not a literal field-for-field swap: it is to preserve what the original creature or character was designed to do at the table, then rebuild it correctly inside the target system's own maths and terminology.

{SOURCE_SYSTEM} is the system the stat block currently uses. {TARGET_SYSTEM} is the system to convert it into.
</context>

<paste>
{STAT_BLOCK}
</paste>

<task>
**Convert the pasted stat block from {SOURCE_SYSTEM} to {TARGET_SYSTEM}:**
1. Identify the creature or character's core role at the table (bruiser, controller, skill monkey, boss encounter, and so on) and its rough power tier
2. Rebuild ability scores, defences and hit points using {TARGET_SYSTEM}'s own maths for that power tier, not a direct numeric copy
3. Recreate special abilities and actions using the closest native {TARGET_SYSTEM} mechanic, and flag any ability that has no clean equivalent
4. Preserve the narrative flavour and any signature move that defines the creature at the table
Work only from the stat block provided. If the source block is missing information a full conversion needs (for example no stated challenge rating or level), state the assumption you made plainly rather than inventing precise numbers and presenting them as given.
</task>

<output_format>
A complete stat block formatted in {TARGET_SYSTEM}'s standard layout and terminology, followed by a short "Conversion notes" section (three to six bullet points) listing every ability that had no direct equivalent and the design choice made instead. Keep total length proportional to the source block; do not pad.
</output_format>