The Headless Horseman can be summoned and looted once per character per day, and Hallow's End lasts about 14 days. That single rule is the whole service: your total number of chances at The Horseman's Reins equals characters x days, so one character gets roughly 14 rolls while ten characters get about 140. We farm every character you list, every day the event is up, for $19.04 per character — which works out to about $1.36 per Horseman kill.
Where he is: the Headless Horseman is summoned from the pumpkin shrine in the Scarlet Monastery Graveyard. Any level 70 group clears him in a few minutes, so the bottleneck was never difficulty — it is the daily lockout on each character.
We do not quote a drop rate for The Horseman's Reins, and you should distrust any page that does. Blizzard has never published one. Every percentage you see is community-aggregated loot data, not an official figure. What is certain is that the reins are a 100% speed ground mount, and that the only lever you control is how many rolls you take before the event closes.
The same bags also hold the Sinister Squashling pet and the Hallowed Helm, plus the Hallow's End achievement items, so nothing is wasted on a day the mount does not land.
Order early. The event is a fixed window: once it ends there are no more summons until next year, and a character added on day 10 can only ever take four rolls.



