How Does a ‘Sybil Attack’ Relate to the Need for a Costly Mechanism like PoW?

A Sybil attack is when an attacker creates numerous fake identities or nodes to gain a disproportionate influence on a network. Proof-of-Work (PoW) combats this by requiring computational work and energy expenditure for each node to participate in block creation.

This cost makes it economically infeasible for an attacker to create and operate a majority of fake, high-power mining nodes. The cost of participation is a key defense against Sybil attacks.