Stake-based multiparty cryptographic primitives operate in a setting where participants are associated with their stake, security is argued against an adversary that is bounded by the total stake it possesses —as opposed to number of parties— and we are interested in scalability, i.e., the complexity of critical operations depends only logarithmically in the number of participants (who are assumed to be numerous). In this work we put forth a new stake-based primitive, stake-based threshold multisignatures (STM, or “Mithril” signatures), which allows the aggregation of individual signatures into a compact certificate provided the stake that supports a given message exceeds a stake threshold. This is achieved by having for each message a pseudorandomly sampled subset of participants eligible to issue an individual signature; this ensures the scalability of signing, communicating the signatures, aggregating them to a certificate and verifying it. We formalize the primitive in the universal composition setting and propose efficient constructions for STMs in the unstructured reference string model. We also showcase that STMs are eminently useful in the blockchain setting by providing three applications: (i) stakeholder decision-making for Proof of Work (PoW) blockchains, specifically, Bitcoin, (ii) fast bootstrapping for Proof of Stake (PoS) blockchains, and (iii) proofs of data availability for consensus scaling.