Polypheny is an adaptive database system using innovative ideas to jointly manage data in multiple models. It bridges the gap between polystores and hybrid transaction/analytical processing (HTAP) systems. In contrast to most existing polystore systems, Polypheny offers support for data manipulation queries. Furthermore, it features a flexible schema, supporting schema changes at runtime. Polypheny is a full database management system providing support for a rich set of data types. Due to its support for features like the enforcement of constraints, transactions, prepared statements, and batch queries, it even goes beyond of what many well-known DBMS provide. Moreover, Polypheny comes with integrated support for several specialized database management systems. Therefore, it is able to efficiently process heterogeneous workloads. The seamless combination of data replication and data partitioning allows combining different underlying data storage engines in order to provide excellent query performance independent of the type of workload. Polypheny even goes a step further in terms of flexibility: With "Data Sources" it is possible to map data on (remote) database systems into the schema of Polypheny. It also features adapters for directly querying CSV files or file systems. Thanks to GSoC 2021, Polypheny now even has support for querying the Ethereum Blockchain. The JDBC, Python and REST query interfaces allow to easily integrate Polypheny into existing environments using industry standard techniques. It supports a broad spectrum of query languages including SQL, CQL, the MongoDB query language and the Pig query language. The powerful browser-based user interface makes managing Polypheny a pleasant experience. In conjunction with the support for multimedia data and workloads, Polypheny offers a flexibility not matched by existing database systems.