Pestilence deals disease damage overtime to a target. When that target dies, if pestilence was still active, it spreads to 2 nearby enemies. Pestilence continues as long as there are nearby enemies and they are killed before its duration expires.
The above disease damage amounts (?, -, 284-347(95-116), 331-404(110-135), 378-462(126-154)) are with STR 80 (no worn armor or items, no buffs and no AAs)