Forrest

This build will require a number of sacrifices but works wonders for Forrest if you are willing. Giving him access to a wrathful/dazzling staff combo, he can effectively ignore his low speed investments. Trilemma+ will allow him to aid other team members significantly as well. Panic ploy allows him to reverse units bonuses, in many cases allowing him to double more average speed units. Resistance ploy works in tandem with Panic ploy, meaning he will be able to deal good amounts of damage, possibly lethal damage too, if positioned properly. Physic works with his cavalry movement capabilities and is in his base set, his special allows him to heal those he can't reach when prevented by the map.

Forrest is a cavalry staff unit who sports impressive HP and the highest Resistance of his class, while having either middling or low amounts in the rest of his stats. 32 Attack is relevant for staff cavaliers, but his Speed is too low for him to reliably make follow-up attacks. Overall, Forrest is a more min-maxed version of Valentine's Silque, who was released only 2 months prior.

Weapon: Dazzling Candlelight+ / Dazzling Rapport Wand+ / Dazzling Toasty Skewer+
While Forrest may be best used as a support unit, his capabilities of helping his allies out on the battlefield is extensive thanks to the variety of weapons he has access to. Candlelight is a great staff for Forrest to use, as its effect allows him to mitigate counterattacks after combat, which is great for helping neutralize tough foes that his allies may have trouble dealing with normally. While using it offers unparalleled utility, it is a fairly uncommon staff, only coming on Mikoto (as Flash) and Bridal Lyn. There are several alternatives to choose from, namely the Rapport Wand and Toasty Skewer. The Rapport Wand grants the fastest ally additional Attack and Defense from anywhere on the map, which can synergize with skills like Spd Opening, while Toasty Skewer stacks well with Close or Distant Guard for a set that focuses on defensive buff stacking, which is great for tanky units. Forrest has no shortage of avenues when it comes to picking a staff to equip him with.

Assist: Restore+ / Recover+ / Physic+
Having a unit be struck with penalties from skills like Aversa's Night, Iago's Tome, or Ploy skills can be inconvenient at best and composition-breaking at worst. Restore allows Forrest to nullify this threat to his allies, which can be invaluable in situations where every move matters. Recover is a different Assist skill that Forrest can use. It heals the most amount of HP per use; while not as exciting as its alternatives, the effect is straightforward, reliable, and easy to fit into any team. The last alternative to consider is Physic. While it heals for less than Recover—as most, if not all, other healing Assists do—it is important to recognize the unmatched range that means Forrest doesn't have to be right next to his allies at all times. With the limited space that each map provides, having one space to have a refresher grant that ally another action or a ranged ally to land a crucial blow on a tough melee opponent can be the difference between victory and defeat.

Special: Earthwater Balm+ / Windfire Balm+ / Heavenly Light
The Balm family of Special skills has proved to be one of the most widely applied and most effective for healers of any and every type. Offering stat bonuses to all allies for a turn can make defeating certain foes possible or saving an imperiled ally. Earthwater Balm, which raises both the Defense and Resistance of all allies, is suitable for defensively-oriented units, while the Windfire variation can push high-power offensive units even further into their specialty. Balms are often quite hard to obtain—only on a handful of healers—so Forrest's default Heavenly Light is a suitable alternative.

A: Fort. Def/Res
While his Defense may be unremarkable while unmerged, Forrest can reach high defenses with enough investment and care. With merges, dragonflowers, and Fort. Def/Res 3 to boost his stats, Forrest can not only protect himself from any damage he may take from melee foes, but also use his fantastic Resistance to debuff opponents, utilizing Sabotages or Ploys.

B: Wrathful Staff / Sabotage Atk or Res
While preventing a foe from counterattacking thanks to the Dazzling Staff effect that can be refined onto any staff can be helpful, Forrest won't get very far if he needs to attack someone because of the naturally subpar offenses of staff users. Wrathful Staff compliments Dazzling Staff to make a potent combination. Forrest can also run a Sabotage instead, which plays off of his naturally high Resistance to inflict penalties upon foes from near or far.

C: Close or Distant Guard / Atk/Spd or Def/Res Gap / Atk or Spd Opening
The Guard family of skills grants nearby allies extra defenses when they go up against either melee or ranged foes, which can be useful for buffing allies from a safe proximity. Guards also go well with Physic, given that Forrest will be able to heal and provide buffs within the same range. Alternatively, Opening skills give Forrest the freedom to be anywhere on the map and still provide bonuses to a certain stat. The only problem is that Openings only affect one stat, which is why Gaps, if available, are a much more suitable skill to run, given their twice the effectiveness of Openings. Pairing a Balm Special with the complementary Opening creates one striking combination.

Sacred Seal: Close or Distant Guard
Stacking the same Guard to offer 6 points of extra defenses to allies within a close proximity of Forrest. Combining a Close and Distant Guard to offer half of that to allies, but more consistently is yet another thing to consider when deciding what Sacred Seal to give Forrest.