Catamaran: Ally Mechanics

Yeah, I'm posting a lot of Catamaran stuff this week because we're starting up again after a few weeks off due to family events and hurricanes. All that time has given me a chance to catch up with some of the rules I've been meaning to write to cover things that have come up in game.

One of these is a better way handle NPC allies in combat as the group of 6-8 PCs has accumulated twenty some odd NPC followers (3 from the Paladin's Noble background, one Paladin in training, one Monk in training, one old shipwright, and twenty one Vikings on the wrong side of the planet that were brought here as prisoner soldiers by one of the bad guy groups in the setting and freed by the players). There have been several situations, particularly on the party's ship where rolling for this mass of humanity was just overwhelming, so it kind of got forgotten. But I don't want them to be forgotten; the players have put a lot of effort and resources into recruiting some of these NPCs and I want it to pay off. They build a bigger boat largely to cart these guys around! While on the ship tasks like manning ballistas and such does alleviate some need for the NPCs to do something, it was not enough, so I came up with the following system after reading Harbringer of Doom's post about a similar idea a few months back.

In order to speed up combat, non-essential NPC allies will not function independently of the PCs, but instead "attach" to the players, granting buffs to PC actions rather than taking their own actions. This does not change the space the PC occupies (but we play loose with our maps and don't use a strict grid so this works for us).

Attaching requires the PC that the NPC is attaching to do spend a bonus action, but a single bonus action can attach multiple NPCs of the same group (so you must spend a bonus action to attach Hakon to you, but you can spend one bonus action to get three of the unnamed Vortlanders with you). You can only have a number of NPCs attached to you equal to your proficiency bonus plus your Charisma bonus.

I tried to have most of the NPCs have some sort of disadvantage, such as reducing movement or disadvantage on a skill, as long as they are attached to make the choice of attaching more interesting. The Vortlanders don't have this because attaching them means risking real damage to the effectiveness of the ship if they are rendered inactive (see below).

The NPCs with the group grant the following bonuses:

• Siewal (Kel’s Squire): Gain 10 temp hit points, recovering from disarm or changing weapons is a free action, attacks of opportunity against you have disadvantage, disadvantage on your Stealth checks
• Taben (Kel’s valet): Gain 3 temp hit points, Advantage on Healing and Persuasion checks, advantage on saves against charm effects, disadvantage on your Intimidation checks
• Oska (Kel’s advisor): Gain 3 temp hit points, Advantage on History and Arcana checks, can spend a bonus action to double spell range, once per battle as a bonus action you can hand off a concentration spell to Oska so she can maintain it without the player character needing to, reduce your movement by 10 ft (she’s old)
• Helsar (Paladin in Training): Gain 5 temp hit points, once per battle can heal 5 hit points or 1 disease/poison as a bonus action, advantage on Nature checks
• Geph the Scalefolk (Monk in Training): Gain 10 temp hit points, Advantage on Athletics checks, when hit with a weapon attack use a reaction to reduce damage by 1d8
• Hakon (Viking Healer): Gain 10 temp hit points, Advantage on Religion and Medicine skill checks, treat 1s and 2s as 3s on any healing dice used on you, advantage on saves against frighten effects
• Steinar (Viking Warleader): Gain 10 temp hit points, advantage on Perception checks, you can make a melee attack as a reaction to being hit in melee, advantage on saves against frighten effects
• Vortlander (Vikings): Gain 5 temp hit points, advantage on saves against frighten effects

If the temp hit points granted by an NPC are used up in a fight, the NPC cannot attach again (including to the ship) until the group has taken a long rest. I'm considering a system where NPCs that lose all their hit points have to make some sort of death save or die, but that seems to harsh.  Another option is requiring a death save if the player they are attached to makes a death save, and if the NPC fails it they die.

Alternately they can attach to the ship and are assumed to be attached to the ship if they are not attached to a player.

• Between the Vortlanders and Geph there are 23 skilled sailor NPCs. If enough NPCs are attached to PCs that eight or fewer are left to crew the boat, the boat is undermanned and suffers disadvantage on all checks, plus -5 ft speed penalty per crewmember missing. 
• Every three NPCs over the nine minimum to crew the ship will allow one ballista to fire every other round. Thus 18 NPCs are needed to crew the ship to full effectiveness and keep all three ballistas manned. 
• Every NPC above the 18 minimum adds +1 to proficiency (water vehicles) checks for the ship or +1 to ballista attacks (which are currently at +4 to hit and do 6d6 damage).