From the white paper:
(1) "As well as offering the services integrated in its own blockchain, Stratis will specialise in providing hosting and consultancy for decentralised applications (Dapps) on top of the Ethereum blockchain." (2) "Stratis will enable one-click provisioning of other major blockchain platforms aside from its own, including Bitcoin, Ethereum, BitShares and LISK”
Stratis is mainly a BAAS (Blockchain As A Service) company.
Stratis appears to be a platform built using forked bitcoin components, with some disassembly and reassembly involved, with a Proof of Stake consensus mechanism thrown in, and with emphasis on use of C# for ease of enterprise adoption.