Once the Zombie Invasion starts, numerous invading zombies will appear in the World Map.
Kill the zombies to gain resource rewards, courage medals and to spawn Zombie Boss that carry huge rewards.

After Season 2 the event evolves, adding a new goal, check it out in this paragraph: Zombie Invasion – Glacieradon

Contents

Introduction

Below you can see how invading zombies and Zombie Boss appear from close.

Goals

There are multiple goals in this event:

• Collect courage medals : –
  • killing Invading Zombies and Zombie Bosses.
  • spend courage medals in the event Trade Store
• Kill Invading Zombies:
  • they provide lot of resources and 10 courage medals
  • all Invading zombies are Level 10 and have all the same amount of rewards.
• Kill Zombie Bosses:
  • they provide lot of resources and more courage medals .
  • the amount of resources and courage medals increase with the Level of the Zombie Boss.
  • the higher the Level the more difficult it is to kill it.
  • if you discovered the Zombie Boss killing an Invading Zombie, whenever the Zombie Boss gets killed by you or anyone else you will receive additional rewards in your mail
• Rank high in the event Leaderboard to earn additional rewards
• After Season 2 an additional alliance goal is added check it out in this paragraph: Zombie Invasion – Glacieradon

Rules

• Killing invading zombies grants “Courage Medals” . Use them to redeem for a variety of rewards at the event store.
• There’s a small chance that a Zombie Boss will appear after killing invading zombies. They offer rich rewards but are very powerful, you will need to rally troops to defeat them.
• During the zombie attack, the damage commanders inflict on the Zombie Boss will be accumulated and ranked. At the end of the event, rewards based on ranking can be claimed in the mailbox. The higher the cumulative damage, the better the rewards.
• After the event ends, commanders who participated in defeating the invading zombies will receive Invasion Defender rewards.
• Once a Zombie Boss appears there is a protection period where only the discoverer’s alliance members can rally against it for 10 minutes

Summoning level rules:

The level range for summoning zombie bosses is determined by the commander’s own “summoning level”, ranging from 15 levels below to 5 levels above the “summoning level”. The higher the level, the lower the probability.
 
The initial summoning level is 5, and there are two ways to increase it:

1. When summoning a zombie boss with a level higher than the current ‘summoning level’ and the leader is killed (regardless of whether the summoner is involved), the ‘summoning level’ is updated to the boss’s level
2. When leading a team to kill a zombie boss higher than the “Summoning Level” (regardless of their level or whether they are the summoner of the leader), the “Summoning Level” will be increased by 5 and can be triggered 3 times during each activity period
   Cross activity inheritance of “Summoning Level” (only increasing and not decreasing throughout the entire lifecycle)

For example, if my summoning level is level 25, the leaders I can summon will randomly appear in levels 10-30 until one of my summoned leaders at level 30 is killed, or I can lead my team to kill one leader at level 25 or above (3 times per activity), then the summoning range will increase to levels 15-35.

( Thanks to CaptFelony for forwarding this info from customer support to me)

Trade Store

The event trade store allows to redeem many interesting items, but they are limited.
Some items appear with Season 1 / Season 2, and they are not immediately available.

My suggestions, mostly for free to play, are to purchase in this order:

• Stamina
• Legendary Gold chest
• Universal Exclusive Weapon Shards
• Drone parts
• Purple Gold chest

The Trade will show additional items based on the Server age, for example once you enter Season 3 pre-season also Oil will be available:

Game play video

Leaderboard and rewards

Zombie Invasion – Glacieradon

Once you passed Season 2, the event evolves adding a new challenge that needs to be addressed by the Alliance.

Additional Rules:

• Defeating the Zombie Bosses earns Glacieradon points for your Alliance. Once enough points are gathered, the Alliance leader and R4 can trigger the Glacieradon challenge manually. Each Alliance can only begin the Glacieradon challenge once per event. Glacieradon uses ice attacks that freeze commander bases, preventing relocation or rallying. The challenge lasts 60 minutes, and if not completed in time, Glacieradon will leave.
• You can attack Glacieradon up to 30 times during the event (30 hits for each commander). Every successful attack reduces Glacieradon’s HP and may trigger a critical hit that deals multiple times the damage. After each attack, players receive the attack reward, and critical hits provide multiplied attack rewards based on the multiplier. The player who lands the final blow will get a 10x attack reward!
• If Glacieradon’s HP drops to zero during the challenge, it will be defeated, and its treasure will drop. Collect it to earn rewards. Note: New Alliance members cannot collect treasure within 24 hours of joining.
• If Glacieradon is defeated within the time limit, all Alliance members will receive a reward via mail. If not, a consolation reward will still be sent. You can only get the rewards once during the event.
• Glacieradon will leave 2 hours before the event ends, and no new challenges can be started after it’s gone. Plan your challenges carefully.

Once the R4/5 starts the event you will see a notification in your Alliance chat, and a Glacieradon in Alliance Finding section of the Zombie Invasion event page. As you can see in this case it is a Level 1 Glacieradon, so expect them to become stronger in the next events.

Clicking on the notification or the Glacieradon icon you can find it on map:

Every 30 seconds (at least at Level 1 Glacieradon) the Glacieradon will attack firing 3 snow balls that will freeze immediately the bases they hit:

Once the monster is killed some Glacieradon’s Treasures appear on map to be collected, similar to Loots when a City is captured.

Additionally if your Alliance manages to kill the Glacieradon, you will receive by mail some rewards (this mail is for a Level 1 Glacieradon):