Gen 9, Tera Raid supporter
Arboliva @ Light Clay
Ability: Seed Sower
Tera Type: Bug
EVs: 252 HP / 252 Def / 4 SpD
IVs: 0 Atk
Calm Nature (+SpD, -Atk)
- Reflect
- Light Screen
- Safeguard
- Pollen Puff
This build provides general-purpose defensive support and healing for Tera Raids. It works against opponent physical attackers, special attackers, hybrid attackers, and even status-inflicters. It also works regardless of the opponent's type and ability, since none of this Arboliva's attacks depend on targeting the opponent or changing stats (either your opponent's or your allies').
Seed Sower (ability) provides passive healing for everyone, halves damage from several common Ground attacks (e.g. Earthquake), and is activated/reactivated automatically upon receiving direct damage (i.e. without having to spend a turn using a move).
Reflect (move) and Light Screen (move) each decrease the damage from a certain category of attack for everyone on your team by 50%. You may choose to use only one or both, depending on the opponent. Either way, Light Clay (item) makes the screen(s) last 8 turns. Moreover, screens are not removed when a Tera Raid boss removes its own negative effects or removes you and your allies' positive effects. Neither are screens prevented from being set when a Tera Raid boss has its shield.
Safeguard (move) is a pseudo-screen that prevents you and your allies from being given any non-volatile status condition (including confusion) by the opponent. Unfortunately, it lasts for only 5 rounds since Light Clay doesn't extend Safeguard (unlike Reflect and Light Screen). However, Safeguard does have all the other benefits like a screen (e.g. it can't normally be removed by Tera Raid bosses; it can be set even when a Tera Raid boss has its shield; etc.).
Pollen Puff (move) is technically a damaging attack (i.e. it can be used when you are Taunted), but its purpose is to heal your allies. When Pollen Puff targets an ally, it heals that ally by 50% of its max HP. You should use Pollen Puff when only one ally needs healing (so that you don't have to waste a multi-ally "Heal Up" cheer), when you are out of "Heal Up" cheers, or whenever you already have screens up.
Regarding stats, this build has the EVs and nature to maximize survivability in the face of both physical attackers and special attackers (and especially hybrid attackers). At level 100, this Arboliva will have 360 HP, 279 Def, and 280 SpD (including EVs, IVs, and the Calm nature). If you are building this Arboliva for a specific purpose (instead of general-purpose or hybrid), feel free to change the Def/SpD ratio and nature to maximize only Def or SpD instead of both simultaneously. Either way, Atk should be minimized to mitigate damage from the occasional Foul Play. Finally, SpA does not warrant EV investment since Pollen Puff heals exactly 50% of the target's max HP when you target an ally, regardless of your SpA.
Note that whenever you already have screens up, there may be nothing else for you to do except Pollen Puff. However, even if your allies are already at full health, it is still more beneficial to use Pollen Puff to target an ally for proactive healing than to target the opponent for damage. This is because by the time Arboliva uses Pollen Puff, your allies will likely have taken damage and will need healing -- Arboliva is quite slow, so you should try to anticipate the need for healing in advance!