Group template
Using groups is a way to make larger numbers of less intimidating creatures more viable to powerful heroes by simplifying the combat. It's considered that the group makes multiple actual attacks or other actions, but use fewer and more likely-to-hit dice rolls instead of rolling a multitude of dice. Similarly for saves such as a dexterity save is more likely to be effective as individual members may be downed instantly, but then covers for others.
Applying a group template is for a creature type large enough to have their own stat block. It's simply more of them grouped up than multiples of a weaker or smaller creature. So packs of rats or wolves could be a group, or a small guard squad could be one. The statistics reflect the members helping one another by making multiple attack attempts, exposing weak spots or to protect each other. Working closely together like this doesn't require as much space to position in combat and consider individual members at times may weave in and out of their main formation which can help them reach foes further away or avoid getting cramped by a foe.
Group traits
The group is a unit of several members joining together making it count both as the group unit as well as individuals. A group can alter its formation as long as total movement doesn't exceed the group's movement and it can move through any opening large enough for a member of the group, but treat any opening smaller than a group member's normal square size as difficult terrain.
Treat the killing of an individual (even if it's multiple individuals) as a direct decrease the group size and remove one instance of base creature HP from the pool, but if a single attack doesn't do enough damage to down a "whole member", the damage is instead distributed in the group HP pool. Any one specific-target attack or spell can at most deal damage equivalent to the Base Creature to the group. Area damage is applied to the group HP pool.
Single-target attacks or spells only deal full damage to one member, dealing one base creature HP to the pool. If enough damage is dealt to down more than one, deal half of the remaining damage to the group HP pool. At DM defined intervals (members downed or group HP pool total lowered), the group's bonuses and actions should be lowered to reflect its loss of fighting capability. Two smaller groups can also join up to count as a larger group, if it's advantageous, or they can split up.
For spells and saving throws, the group is immune to many conditions but the individual members are not. Treat any spell that downs or incapacitates an individual similar to downing a member with an attack, though they potentially can rejoin later. The group can only regain hit points up to the maximum of numbers of active members' base creature HP combined, and for each application, at most a base creature's HP minus one. If a spell would give temporary HP to multiple targets, add those multiples of temporary HP to the group HP pool unless the same individual would be targeted more than once.
Apply Template
- Consider feasible maximum group size for a majority of members to actually be effective before making the group and tiny or large creatures may be a bad match
- Add up HP for all creatures in a group HP pool
- Lower movement speed by 5 if it was 30 or lower, by 10 if it is faster than 30 and by 20 if it's 65 or faster
- Determine size: 1 square for each 2.5 medium (x0.4) or 5 small members (x0.2). (10-20 tiny members depending on size, or 1.5 large or larger in a standard area).
- If a second square is added it may be applicable to add +5ft reach for members lunging towards enemies but probably not more than that
- Add Condition Immunities: Charmed, Frightened, Grappled, Paralyzed, Petrified, Prone, Restrained, Stunned
- Add bonus action options: "Perform an action that does not include a damage attack." And: "Use four bonus actions to take an attack action."
- Group Bonus is +1 for every member up to 5, then +1 for every additional three (round up).
- Add the Group Bonus to to-hit, damage, Str/Con-checks and Str/Con-saves.
- Add multiattack use if there are 4 or more members
- Add one bonus action and one reaction for every 5 members
- Add half the Group Bonus to AC, up to 18. If the base creature would gain no benefit, it gets at least up to +2.