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Mechs are immense, anthropomorphic robots that combine armor, agility, and
firepower into one devastating package piloted by one or more operators. Although
mechs were originally developed as weapons of war and remain popular in many
armies, the technology has dispersed to less militant organizations, inspiring
models better suited for exploring dangerous environments, performing heavy
labor, and more. In Starfinder, mechs represent powerful tools for PCs to confront
far mightier foes than they could unaided. The PCs might custom build their
own mechs, salvage the technology in the field, or pilot mechs provided by powerful
Mech combat is a flexible system. Mechs use many of the existing rules for Starfinder, allowing players to jump into the action quickly— whether they’re clashing with other mechs, powerful creatures, or entire squadrons of foes. Building mechs presents a wide array of options, allowing players to customize their mechs’ limbs, size, armaments, and more. The system also allows the PCs to pilot one big mech, each create their own mech, or split between several machines in any combination.
Unlike powered armor, which is an extension of the user’s body that deflects attacks rather than absorb damage, a mech functions more like a specialized vehicle piloted by one or more operators. Each mech has its own defenses and Hit Points, shielding its operators from harm while they give the mech commands. Mech weapons are in a class of their own, far exceeding in scale any armaments sized for PCs.
Much as with acquiring a starship and including starship combat in adventures, acquiring mechs does not typically cost the PCs credits, and Starfinder campaigns can thrive with any amount of mech combat, from mech encounters every session to no mech combat whatsoever. The exact prevalence of mech encounters depends on the campaign and is ultimately up to the GM to decide; in a typical campaign, mechs are not available for sale. By their nature, mechs provide a significant power advantage that make many otherwise challenging encounters trivial, so GMs can best include mechs in the game purposefully—as a way to overcome otherwise impossible odds or insurmountable foes, for example—rather than to trivialize challenges the PCs face.
Mech combat is designed to function on the same scale and with the same overarching
rules as most other Starfinder combats, using the same square-grid maps, means
of resolving attacks, and more. As a result, designing encounters with and for
mechs is not substantially different than designing for encounters with smaller
participants. Take the following into account when designing encounters for
CR: Mechs are powerful. PCs that are operating mechs appropriate for their level have an Average Party Level 3 levels higher than normal. This allows them to overcome stronger threats as a result, with a few considerations. First, mechs with multiple operators are typically highly maneuverable, capable of moving and attacking easily. This makes slow-moving foes with limited ranged options far less threatening, for PC mechs can often run circles around them. When presenting a small number of foes, either favor maneuverable or long-range combatants, or consider providing terrain or objectives that encourage the PCs to engage the enemy directly.
Second, many mech weapons excel at attacking multiple targets at once, so while mechs can comfortably fight one powerful foe, they excel at fending off large numbers of lesser foes. Enemies whose CR are lower than the mech’s tier rarely pose a significant threat to that mech except in large groups. However, using a few mechs to defeat a small army—or a large foe with numerous minions—can be very gratifying.
Experience: Even though the PCs overcome much more powerful threats, mech encounters should provide a similar amount of experience to other encounters for the PCs’ level. Combat encounters the PCs overcome while using mechs typically grant experience points as though the CR of each foe and other challenge were 3 lower than usual. Do not reduce the experience points earned from challenges that aren’t substantially affected by the PCs’ access to mechs, such as story awards for performing heists or overcoming encounters peacefully.
Space: Mechs are big. Huge mechs might be able to navigate some conventional adventure spaces, but Gargantuan and Colossal mechs require a large area to maneuver and fight effectively. When creating mech encounters, aim to provide each mech at least four times as much area to maneuver in than the mech occupies, and make sure any paths, halls, or other passageways are large enough to accommodate the combatants. Alternatively, if the goal is to create an encounter where the mech struggles to maneuver or engage foes due in part to restrictive terrain, consider treating the encounter’s Challenge Rating as at least 1 lower. An encounter in which the PCs fight an immense foe by exploiting constricting terrain can be a fun encounter!
As a GM, you can create mech combatants to challenge the PCs using the rules
in the Building a Mech section on pages 15–25. When doing so, calculate a mech’s
challenge rating by adding 2 to its CR if it has one operator, 3 to the CR if
it has 2–3 operators, and 4 to the CR if it has 4 or more operators. Be aware
that mechs designed in this way have statistics best suited for PCs, and as
a result such mechs have fewer Hit Points, stronger defenses, lower attack bonuses,
and slightly lower damage per attack than a creature of comparable CR.
As a recommended alternative, use the following rules to create NPC mechs that are both quicker to design and better designed for use as antagonists. These rules borrow many of the modifiers, values, and design recommendations from Appendix 1 of Starfinder Alien Archive, especially the Everything Is Optional sidebar on page 127. If you want a mech that feels faster, hardier, or more deadly, adjust the numbers slightly for a few statistics, and consider reducing a few other statistics to compensate.
Challenge Rating: Select the mech’s CR. Remember that PCs in their own mechs are much stronger, and an enemy mech’s CR must be approximately 3 higher than normal to provide an equivalent challenge.
Operators: Because a mech’s number of actions depends on its number of operators, an NPC mech’s statistics depend on its number of operators; a larger number of operators results in the mech having lower bonuses to compensate. Use the instructions below for a mech with 1 operator. For a mech with 2–3 operators, treat the mech’s CR as 2 lower for the purpose of calculating its attack bonuses. For a mech with 4–6 operators, treat the mech’s CR as 3 lower for the purpose of calculating its attack bonuses.
Statistics: Follow the instructions for building a creature, using the EAC, KAC, saving throw bonuses, attack bonuses, and ability DCs for a creature of the chosen CR. Use the skill bonuses for a creature whose CR is 3 lower than the mech’s CR. NPC mechs use the combatant array (Alien Archive 129–130).
Hit Points and Shield Points: Use the listed number of Hit Points for a creature whose CR is 2 lower than your mech’s CR. Give the mech a number of Shield Points equal to one-fifth the mech’s Hit Point total. Each turn, the mech regains a number of missing Shield Points equal to its CR.
Weapons and Damage: Rather than use the damage listed in the combatant array, give the mech several mech weapons (pages 20-24) whose levels are each 3 lower than the mech’s CR (minimum 1). A typical mech should have weapons whose combined Mech Point cost per level is approximately 9, providing it about three weapons. Use the weapons’ level and type to determine their base damage dice, per Table 2–3: Weapon Damage on page 20. For ranged weapons, add the mech’s CR – 3 (minimum 0) as a damage modifier. For melee weapons, add an additional damage modifier of 5, representing the mech’s extraordinary strength.
Hardness: The mech has a hardness value equal to half its CR, rounded down.
Speed: A typical mech has a speed of 40 feet. Optionally, increase the mech’s speed by up to 40 feet, give the mech a fly speed of 60 feet (average maneuverability), or a swim speed of 60 feet.
Power Points: A typical mech begins an encounter with 3 Power Points (page 13), regains 1 PP per turn, and can store a maximum of 5 PP.
Auxiliary Systems: The mech can select up to 4 auxiliary systems. Depending on the role the mech plays in the encounter, it might not need all of these systems. In general, limit the mech to one auxiliary system that is restricted to a particular mech frame, such as a cloaker or teleporter.