Portland HODL explores "poison blocks" - a vulnerability in Bitcoin where malicious miners can craft blocks that take excessive time to validate (25+ minutes on modern hardware, 11+ hours on a Raspberry Pi). The demonstration reveals how quadratic hashing vulnerabilities and signature validation can be exploited to essentially "DOS" Bitcoin nodes, rendering them useless during validation. While difficult to execute without mining power, the attack highlights the need for potential consensus changes like the "great consensus cleanup" to prevent network disruption. An eye-opening look at Bitcoin's validation challenges. Alt title: "The Mempool Anarchist's Cookbook"