The Hydro Tulpa is a Field Boss introduced in Genshin Impact, particularly associated with the Hydro-themed region of Fontaine. Here's a detailed overview.
Image via HoYoverse.
The Basics
•Appearance and Lore: The Hydro Tulpa manifests as a spectral, water-formed entity with a humanoid or sometimes animalistic shape, embodying the concept of Tulpas, which are thought-form entities in esoteric traditions. Its body constantly shifts and flows, reflecting the ever-changing nature of water.
•Location: Fontaine Region: This boss is found in a special area within Fontaine, possibly near significant bofors of water or in a location connected to Fontaine's Hydro-related lore.
Combat Mechanics
Phases
•Initial Phase: It starts with a watery form that must be disrupted to reveal its core or true form.
•Elemental Shift: After disrupting its form, it might shift between various Hydro-based attacks, perhaps even temporarily harnessing other elements but with a focus on Hydro.
•Regeneration: At specific health thresholds, it might attempt to regenerate or change its form, which can be interrupted for bonus damage.
Attacks
•Hydro Torrents: Unleashes streams of water that sweep across the battlefield, dealing Hydro damage.
•Water Prison: Can trap players in a bubble of water, restricting movement and dealing continuous damage.
•Spectral Blades: Summons Hydro blades that fly towards players or create Hydro fields.
•Tsunami Wave: A large wave of water that floods part of the arena, pushing players back and dealing significant Hydro damage.
Strategy 
•Elemental Weakness: While inherently Hydro, it might be vulnerable to Electro reactions like Electro-Charged (Hydro + Electro) or potentially to Pyro for Vaporize reactions.
Avoiding Damage
•Use characters with high mobility or those who can manipulate the battlefield like Venti or Jean to avoid being caught in Hydro Torrents or Tsunami Waves.
•Characters with shields, especially those like Zhongli for a versatile shield, can mitigate Hydro damage.
DPS Focus
•Focus on breaking its initial protective water shield, then switch to high DPS characters like Eula or Ayato when it's vulnerable.
Elemental Reactions
•Triggering reactions can not only deal damage but also disrupt its water-based attacks or fields.
•Healing and Shielding: Given its Hydro attacks, having a healer like Kokomi or a shield like Noelle can be very beneficial.
Team Composition
•DPS: Characters like Keqing for Electro or Hu Tao for Pyro can exploit its weaknesses.
•Supports: Characters like Xingqiu for Hydro or Fischl for Electro reactions.
•Healer: Characters like Barbara for healing with Hydro resonance or Diona for Cryo resonance.
•Utility: Zhongli for his shield or Sucrose for Elemental Mastery boost and crowd control.
Rewards
•Defeating the Hydro Tulpa grants:
•Primogems
•Hero's Wit
•Mystic Enhancement Ore
•Talent materials related to Hydro or potentially new materials tied to Fontaine lore.
Tips: 
•Reaction Management: Utilize elemental reactions to control the fight, especially when dealing with its Hydro-based attacks or fields.
•Interrupting: Focus high damage when it attempts to regenerate or use its "Water Prison" to prevent or mitigate its effects.
•Mobility: Stay mobile to avoid its area attacks or to quickly reposition when it shifts between attack patterns.
•Environmental Awareness: Use any environmental features around the battlefield for cover or strategic positioning, especially in a water-themed environment.
The Hydro Tulpa, with its unique mechanics centered around water manipulation and the mystical lore of Tulpas, offers a fresh challenge in Genshin Impact. It tests players' ability to adapt to fluid combat situations while dealing with its Hydro-based abilities, making it a memorable addition to the game's roster of Field Bosses.
