Monster Hunter Stories 3 Guide: How to Beat All Invasive Monsters

Invasive Monsters are one of the most rewarding systems in Monster Hunter Stories 3: Twisted Reflection, but they can also be surprisingly tricky to track down. These are supercharged versions of familiar monsters that have muscled into the habitats of endangered species, and your job as a ranger is to drive them out. Repel each one, and you unlock a den containing a rare Endangered Egg. There are nine Invasive Monsters spread across three major regions, and each one demands a specific repel strategy rather than a simple health-drain victory.

What Are Invasive Monsters and How Do They Work?

Unlike standard boss encounters, you cannot simply whittle down an Invasive Monster's health bar to win. Instead, you need to fulfill specific retreat conditions during the fight. Before each battle, Rudy analyzes Invasive Monster Tracks found near the creature's territory to determine exactly what those conditions are. This means scouting the area before engaging is not optional; it is the key to the entire encounter.

There is another important detail: Invasive Monsters only appear at night. Visit any Catavan Stand on the map and switch the time to nighttime before heading to their territories. If you arrive during the day, the territory will appear empty.

How to Unlock Invasive Monsters

You do not need to go hunting for the first encounter. The Invasive Yian Garuga is introduced automatically during the main quest The Princess of Vermeil, specifically in Act 1, Chapter 6. This story-mandatory fight doubles as a tutorial for the entire Invasive Monster system, introducing the concept of Endangered Species and the egg rewards tied to repelling these creatures.

After that first forced encounter, the remaining eight Invasive Monsters are scattered across the world and must be sought out manually.

All Invasive Monster Locations, Repel Conditions, and Egg Rewards

Here is a full breakdown organized by region:

Azuria Region

Invasive Yian Garuga

This encounter is story-mandatory and serves as your introduction to the system. The Yian Garuga is straightforward compared to what comes later. Focus your attacks on its legs using Slash-type weapons to break them down. Doing so satisfies the retreat condition, and you walk away with a Rathian Egg as your reward.

Invasive Seregios

The Seregios roosts on a cliff in the northern part of Azuria, and you will need a flying monstie to reach it (the territory is only accessible at night). The fight has an interesting reactive mechanic: watch the color of the Seregios's roar, then respond with the matching Perfect Crush attribute using a Hammer.

• Red roar: Perfect Crush with Speed
• Blue roar: Perfect Crush with Technical
• Green roar: Perfect Crush with Power

Surviving until the second turn is also listed as a condition, so do not panic if the first turn feels rough. Repelling it earns you the Astalos Egg.

Invasive Plesioth

Head north of the Mirror Lake Catavan Stand and look for a cave accessible via a swimming monstie. The channel leads directly to the Plesioth's territory. Your strategy here is two-phased: open with Fire-element attacks, then shift focus to breaking its head once it enters its Enraged state. Repelling the Plesioth rewards you with the Lagiacrus Egg.

Plesioth cave territory entrance

Canalta Timberland Region

Invasive Arzuros

Like the Yian Garuga, the Arzuros is a story-mandatory encounter that you cannot skip during the main campaign. The key mechanic here is targeting its Honey Supply, which the Arzuros uses to summon additional Arzuros into the fight. Pair a multi-hit weapon with a Speed-type monstie to counter its strengths efficiently. Clear the summoned Arzuros and destroy the Honey Supply to trigger the retreat, earning the Canyne Egg.

Invasive Shogun Ceanataur

This one is tucked behind a waterfall in Canalta Timberland (see the region map for the exact marked spot). The Shogun Ceanataur hits hard with its Killer Claw attacks, so your primary challenge is surviving the incoming damage rather than dealing it. Stack Defense Up through your monstie and allies, or use Mega Armorskin to create a buffer. The claws themselves are brittle and can be broken quickly once you endure the initial barrage. Repelling it rewards the Mizutsune Egg.

Invasive Nerscylla

Glide east from Camp: Blessing Hill to reach the eastern edge of the Canalta Timberland map, where the Nerscylla's territory sits. The key tool here is a Gunlance equipped with the Wyvern's Fire skill (Wyvern's Blaze also works). Conserve your stamina throughout the fight, then wait for the Nerscylla to turn invisible. The moment it moves in to attack, unleash Wyvern's Fire. Timing is everything here. A successful hit during the invisible approach triggers the retreat and unlocks the Nargacuga Egg.

Tarkuan Region

Tarkuan invasive territory map

Invasive Diablos

From the Lookout Point: Rococo Rocks Catavan Stand, drop to ground level and head southeast. Follow the ravine opening, then climb the wall at the path's end to reach the Diablos. The fight's defining mechanic involves the Diablos burrowing underground and spawning three holes on the surface. Select a hole and perform the Spinning Meteor skill from a Hammer the instant dust begins rising from that hole. Mistiming the strike causes the Diablos to emerge from a different hole and deal damage, so patience matters. Nail the timing, and the Tigrex Egg is yours.

Invasive Odogaron

From the Rococo Rocks Catavan Stand, glide south to find a column with an updraft. Ride it northwest, find the opening in the rocks, follow the path, and climb the wall to reach the Odogaron. Bring a monstie with a Mud move and spam attacks like Mud Torrent to reduce its fire output and break its claws. Once the claws are destroyed, the retreat condition is met and you receive the Zinogre Egg.

Invasive Khezu

From the center of the Tarkuan map, glide over the rocks heading northeast. Hop across the rocks to locate the entrance to the Khezu's territory. The repel condition here is patience-based: wait for the battle screen to display the "Learning Complete" message, then immediately execute a Double Kinship attack. That single well-timed strike is enough to force the retreat, rewarding you with the Barioth Egg.

Why Should You Prioritize Invasive Monsters?

Every Invasive Monster you repel unlocks an Endangered Egg den, giving you access to rare monsties that cannot be obtained any other way. The egg rewards include standout creatures like Lagiacrus, Mizutsune, Zinogre, Barioth, and Nargacuga, all of which rank among the strongest monsties in the game. Beyond the eggs themselves, clearing Invasive Monsters contributes directly to Habitat Restoration for each region, which is a core part of the game's conservation loop.

If you are aiming to build the best possible monstie roster, working through all nine Invasive Monsters is one of the most efficient paths to getting there.