A Quantitative Grouping of Boss Design in Elden Ring: Shadow of the Erdtree, Through Attack Concentration and Preparation Sensitivity

Boss difficulty in FromSoftware games is usually argued about, not measured. This paper analyzes 8,017 recorded player deaths across eight major bosses of Elden Ring: Shadow of the Erdtree, drawn from attempt-by-attempt logs of a fixed panel of fifteen streamers. Rather than ranking bosses by raw death count, a method that mostly measures how often a fight was attempted, this paper introduces two independent metrics computed directly from the data. The Attack Concentration Index (ACI) measures how evenly a boss's lethality is spread across its moveset. Preparation Sensitivity measures how strongly a player's total deaths against a boss correlate with their Scadutree Blessing count, a DLC-specific gear-progression stat. Crossing these two axes produces a four-quadrant typology: bosses whose danger is concentrated in a signature attack and answerable through preparation (Radahn, Putrescent Knight), bosses whose danger is equally concentrated but resistant to preparation (Romina, Messmer), bosses whose danger is spread across the moveset but still gear-sensitive (Bayle), and bosses whose danger is both spread out and preparation-resistant (Midra, Rellana, the Dancing Lion). This typology suggests Shadow of the Erdtree's most-discussed bosses do not share a single design signature, and that the community habit of calling all of them "hard" collapses at least four structurally distinct design problems into one label.