This module uses the zipper initiative as described by @Taking20 in YouTube.

Under zipper initiative, PCs and NPCs are sorted alternating in the initiative order. One (mostly aesthetic) change from @Taking20 is that an NPC will be given initiative equal to the PC that it goes after, instead of one less initiative value. This is primarily to better resolve ties without losing the alternating order, as well as to more easily resolve initiative that uses Dexterity to break ties.

Rules

• Players roll initiative as normal.
• DM rolls initiative for one NPC—--the one with the highest initiative bonus. This is the "NPC leader."
• Determine if the PCs or NPC won by comparing the NPC roll to that of the highest PC roll.
• Assign initiative to rest of NPCs by alternating between PCs and NPCs in the initiative order.

NPC leader

The module will use the following rules to select the NPC leader:

1. If a single NPC rolled manually, it is assumed to be the leader.
2. If multiple NPCs rolled manually, the one with the highest bonus will be the leader. (Note that in this scenario, the leader might not have the highest initiative roll.)
3. If no NPCs rolled, the NPC with the highest bonus will be chosen.
4. If bonus cannot be determined, the NPC will be selected at random from the relevant group.

See the Github page for more details.