A Boost Transform is a hook for a single low level character to get involved in modules scaled for a higher level party. Here’s a quick guide to building one for a specific character.
Boost Transforms can be conceptualized in other forms than as an enchantment which turns a character into another creature. This framework can just as easily be used to create Boost Artifacts or Boost Boons (granted by an NPC). Technically, the Boost can be treated like a Curse of Transformation. (9th ed rulebook p90)
The goal of a Boost Transform is to provide about enough power to let a player face the enemy NPCs on fair terms. It shouldn’t make him the toughest character there. But it should give him a unique trick, a way of supporting his allies, or a cool moment.
A Boost Transform can be measured in terms of how many effective levels it adds. Calculate the level difference between the party and the low level player they’re bringing. If a level 8 character is tagging along with a party whose average level is 28, you can build the Boost Transform with a budget of about 15-20 levels.
Add a certain amount of defense based on the Boost Transform’s level. For each level, add a point of body, physical armor, arcane armor, dexterity armor, body points, or a mix.
For fighters, the simplest route is to add a strength bonus. A quick rule of thumb is to add 2 point of strength for every 3 levels. (roughly equivalent to granting 2 profs at 15 build) If the other fighters on the module can drop a monster in 4 swings, then a boosted fighter should be able to kill it in 5 or 6. A level can also be spent on a parry/slay, 1-3 physical weapon attacks (ie “physical strike flamebolt (20)”), or the ability to swing 10s as a critical attack.
For scholars, the basic idea is to make sure that they can throw a lot of spells without expending all their resources for the weekend. One method is to allow spellcasters to treat the adventure as if it’s a full day of spells. After it’s over, their spell pyramid will return to what it was before they began the module. Another method is to add a pool of of 20 healing or elemental damage per level which they can cast in increments of 5 or 10 at a time, similar to the element’s fury cantrip. You can grant a few times-ever spell-like abilities such as Dragon’s Breath or Cure Mortal Wounds, or allow the caster to regain a certain number of spell slots by meditating after each encounter during the adventure.
Templars Boost Transforms combine the building techniques for fighters and scholars.
Boost Transforms for Rogues are built similar to fighters, but substitute assassinate/dodge and waylay, for fighter skills and grant twice as much backstab damage as you would strength.
A Boost Transform’s stats are clustered around a theme. This often reflects a role in combat such as melee, ranged attacks, healing, buffing, debuffing, or ambush. They usually also incorporate a setting flavor such as golems, fae, necromancy, celestial magic, earth magic, tyrran forces, lycanthrope, or one of the elements.