Aim 

In general, the compatibility between Lancer and Starfinder 2e (SF2e) is straightforward, Lancer when in mech and SF2e when not in mech, but for those cases where they cross over this aims to bridge the gap.  In most cases, Lancer is being added to Starfinder. This is because Lancer has applicable out-of-mech rules while Starfinder does not have applicable in-mech rules; it is therefore easier to add some aspects of pilot play into Starfinder and keep the mech combat mostly separate.  

Scope 

The LSF2e compat aims to cover the downtime, boots on the ground, and mech combat areas of play. Where the area depends on GM choice, there may be suggestions for how to deal with it. 

Setting 

Setting is not my problem. Choose Lancer, choose Starfinder, choose to mash them together or homebrew it; it does not affect the rules in any way (unless you choose it to I guess). 

Disclaimer 

I have played a lot of dnd and pathfinder 2e, I haven't played any starfinder 2e or more than a oneshot of Lancer. I'm making these rules so I Can play Lancer for my next campaign :). My experience is in playing online with VTTs, and this will have affected how I consider the rules and conversion.  

General points 

Below is a suggested table to match the starfinder level to the license level in terms of conversion. It doesn’t have LL0 because I don’t like GMS enough for more than a level. The item/vehicle level of Lancer mechs should be the same as the tier bracket it is in, i.e. LL0-4 mechs are tier 1 are SF2e level 5. Costs of mechs are considered irrelevant in Lancer, but the values suggested for each tier roughly scale as SF2e does. 

Accuracy in Lancer could be carried straight across to become a circumstance bonus to the roll. The table below suggests a flat conversion for number of accuracies/difficulties on the roll to a circumstance bonus. The conversion should be applied after totalling the number of accuracies, i.e. +2 –1 is a +3 not a +1. 

Full characters should be created using both the Lancer and SF2e character creation tools (use pathbuilder and COMP/CON, they are cool and free!). The Lancer character does not need to choose any gear, as this should be used from SF2e. Backgrounds should also be taken from SF2e, although the suggested backgrounds from Lancer are good inspiration if required. 

Triggers can be added to skill checks as a circumstance bonus where appropriate. In combat, relevant triggers can be added to attack rolls using a hero point. 

Downtime 

Both Lancer and SF2e have great options for what to do during downtime, and Lancer especially has a strong focus on letting the players have downtime between missions. The Lancer downtime actions should be available to players in addition to the standard SF2e actions. The player can roll a relevant SF2e skill check against the DC for their level, with the difficulty adjusted as appropriate for the specifics of the action. On a critical success use the 20+ result, on a success use the 10-19 result, and on a failure or critical failure use the 9 or less result. If the pilot has a relevant trigger, this can be added to the skill check as a circumstance bonus to the roll.  As well as the usual rewards like reserves, a downtime action could reward minor (10) Xp or moderate (30) Xp to cover a whole party’s actions. 

Boots on the Ground – Exploration 

Exploration in SF2e covers the time between combat and downtime. It can involve a variety of actions and skill checks. Outside of combat, a relevant trigger can be used to add a circumstance bonus to the roll; For example, the Word on the Street trigger could be added to the Gather Information (diplomacy) or Access Infosphere (computers) exploration activities.  

Combat – SF2e encounters 

Encounters cover combat from SF2e, and these run as normal. Pilot gear, equipment, and skills should all be taken from the SF2e characters. Lancer pilot skill triggers can be applied to checks and attacks as a circumstance bonus using a hero point, which allows pilots to use their skills in important moments without adding a +6 from Assault to every attack. 

Adding enemy mechs to encounters 

Pilot vs mech is almost an inevitability in a game combining SF2e and Lancer, and the option will at least cross the mind of any GM planning a game. The design methodology for the conversion used is that a mech should hit hard, but not well, and be hard to damage with small arms. As an example of the conversion, the stat block for the tier 1 Assault class mech is displayed below. The conversion was designed around the Assault class because it is a good standard mech to start from and is supposedly the most common primary battle frame in the galaxy. 

The base idea is that mech scale is 1d8 larger than pilot scale, and the HASE skills are mapped H-Str, A-Dex, S-Wil, and E-Con. The full conversion is in the table below. 

 Effects that do heat (self) apply the heat as fire damage directly (1:1), bypassing resistances. Effects that apply heat damage to enemies are converted to d8s as normal. Kinetic is physical damage, energy is electricity damage, burn is persistent fire damage, and heat is fire damage. Weapons with inherent accuracy/difficulty add the equivalent SF2e bonus as in the earlier table to the attack roll (so attack roll + tier level + in/accuracy value), any additional accuracies gained from features/traits are added as a circumstance bonus to the attack. To convert action costs a quick action is one action, and a full action is two actions. 

Where optional systems or templates are applied to an NPC class this will affect the equivalent level, working out all those combinations and equivalent level is out of my scope :P. Rank Discipline is on the stat block as an example of applying an optional system but is not part of the standard level 5 mech. Annex A has a conversion for the Tier 2 Assault with optional Micro-Missile Barrage and the Tier 1 Assassin for examples. 

Adding friendly mechs to encounters 

Mech vs innocent space grunts is almost an inevitability in a game combining SF2e and Lancer, and the option will cross the mind of any idiot who took the warthog further than they were supposed to or decided that they paid for the whole Caliban they want to use the whole Caliban. The problem of getting the pilots out of the mechs to do SF2e stuff can be approached in many ways, which is a campaign problem not a compat problem. For friendly NPC mechs use the same class conversion as above, like you would having allied mechs in a Lancer combat. If the whole party wants to bring their mechs when you weren’t planning it, then the options are to convert all SF2e enemies to Lancer enemies (below) or to plan two combats for every fight depending on what your party does. However, the Barbarossa is unlikely to fit into the same holes as a Goblin does. If some - but not all - of the party wants to bring their mechs into a fight, then the following options are available.  

First, say no. It is a collaborative storytelling game and sometimes you don’t want to go through all that hassle, an appreciative player will understand that it is more work added to the whole 2 system campaign you are already running.  

Second, convert the mech into a SF2e creature using the table above. The conversion should be done with the equivalent Tier for the mech License Level, but you can also use the LL-SF2e level equivalent if you don’t want to entirely break the balance of your planned encounter by adding a level 5/10/15 problem. For in person play this is a task you can leave to the player who brought their mech to the people-fight, but for VTT players this is a GM task to create a player pilotable monster and should only be done if you really really like them. Structure should be used as normal from Lancer, additional health bars with structure checks in between. After the combat, damage should be converted back onto the mech by dividing the remaining HP by 5 and rounding down. Quick actions are one action, full actions are two actions, and mechs cannot overcharge in combat.  

Combat – Lancer mech combat 

Mech combat covers combat from Lancer, and these run as normal. Mech stats and pilot talents should be taken from the Lancer characters. Nothing from SF2e should be added to mech combat, for the same reason that skill triggers aren’t used in mech combat. Sometimes pilots will feel the need to exit their mech in the middle of the huge battle going on, so here are the rules to convert SF2e characters into Lancer combat. The general idea is that mech scale is 1d8 bigger than pilot scale, so everything a pilot does is reduced by 1d8. 

Pilot actions:  

Fight (full), make a ranged or melee attack or cast a spell. Expend 2 × the expend value if relevant. You cannot Grapple, Shove, or Trip a mech. 

Jockey (full), As in Lancer pilot actions but use an Athletics skill check + Grit. 

Annex A - additional SF2e mech conversions