diff --git a/PFERD/crawler.py b/PFERD/crawler.py
new file mode 100644
index 0000000..9f1c7d9
--- /dev/null
+++ b/PFERD/crawler.py
@@ -0,0 +1,60 @@
+import configparser
+from abc import ABC, abstractmethod
+from contextlib import asynccontextmanager
+from pathlib import Path
+from typing import AsyncIterator, Optional
+
+from rich.markup import escape
+
+from .conductor import ProgressBar, TerminalConductor
+from .limiter import Limiter
+from .transformer import RuleParseException, Transformer
+
+
+class CrawlerLoadException(Exception):
+    pass
+
+
+class Crawler(ABC):
+    def __init__(self, name: str, section: configparser.SectionProxy) -> None:
+        """
+        May throw a CrawlerLoadException.
+        """
+
+        self.name = name
+
+        self._conductor = TerminalConductor()
+        self._limiter = Limiter()
+
+        try:
+            self._transformer = Transformer(section.get("transform", ""))
+        except RuleParseException as e:
+            e.pretty_print()
+            raise CrawlerLoadException()
+
+        # output_dir = Path(section.get("output_dir", name))
+
+    def print(self, text: str) -> None:
+        self._conductor.print(text)
+
+    @asynccontextmanager
+    async def progress_bar(
+            self,
+            path: Path,
+            total: Optional[int] = None,
+    ) -> AsyncIterator[ProgressBar]:
+        desc = escape(str(path))
+        async with self._limiter.limit():
+            with self._conductor.progress_bar(desc, total=total) as bar:
+                yield bar
+
+    async def run(self) -> None:
+        await self._conductor.start()
+        try:
+            await self.crawl()
+        finally:
+            await self._conductor.stop()
+
+    @abstractmethod
+    async def crawl(self) -> None:
+        pass
diff --git a/PFERD/crawlers/__init__.py b/PFERD/crawlers/__init__.py
new file mode 100644
index 0000000..5248a2d
--- /dev/null
+++ b/PFERD/crawlers/__init__.py
@@ -0,0 +1,5 @@
+from .dummy import DummyCrawler
+
+CRAWLERS = {
+    "dummy": DummyCrawler,
+}
diff --git a/PFERD/crawlers/dummy.py b/PFERD/crawlers/dummy.py
new file mode 100644
index 0000000..b4d787a
--- /dev/null
+++ b/PFERD/crawlers/dummy.py
@@ -0,0 +1,53 @@
+import asyncio
+import random
+from pathlib import Path
+from typing import Any
+
+from rich.markup import escape
+
+from ..crawler import Crawler
+
+DUMMY_TREE = {
+    "Blätter": {
+        "Blatt_01.pdf": (),
+        "Blatt_02.pdf": (),
+        "Blatt_03.pdf": (),
+        "Blatt_04.pdf": (),
+        "Blatt_05.pdf": (),
+        "Blatt_01_Lösung.pdf": (),
+        "Blatt_02_Lösung.pdf": (),
+        "Blatt_03_Lösung.pdf": (),
+        "Blatt_04_Lösung.pdf": (),
+        "Blatt_05_Lösung.pdf": (),
+    },
+    "Vorlesungsfolien": {
+        "VL_01.pdf": (),
+        "VL_02.pdf": (),
+        "VL_03.pdf": (),
+        "VL_04.pdf": (),
+        "VL_05.pdf": (),
+    },
+    "noch_mehr.txt": (),
+    "dateien.jar": (),
+}
+
+
+class DummyCrawler(Crawler):
+    async def crawl(self) -> None:
+        await self._crawl_entry(Path(), DUMMY_TREE)
+
+    async def _crawl_entry(self, path: Path, value: Any) -> None:
+        if value == ():
+            n = random.randint(5, 20)
+            async with self.progress_bar(path, n) as bar:
+                await asyncio.sleep(random.random() / 2)
+                for i in range(n):
+                    await asyncio.sleep(0.5)
+                    bar.advance()
+            self.print(f"[green]Downloaded {escape(str(path))}")
+        else:
+            t = random.random() * 2 + 1
+            async with self.progress_bar(path) as bar:
+                await asyncio.sleep(t)
+            tasks = [self._crawl_entry(path / k, v) for k, v in value.items()]
+            await asyncio.gather(*tasks)