How to Get Units in 8 Bit Tower Defense (Summoning Guide)

You get new units by summoning, and summoning lives in the outpost — the game's hub. The ten-pull button on that menu is labeled SUMMON x10 - 500, and every summon adds the rolled units to your roster, with new discoveries recorded in your Index.

Quick answer

Open the SUMMON menu in the outpost and spend Gems. A ten-pull costs 500 Gems, and each summon adds units to your collection with new discoveries logged in your Index.

• Single summons and 10x summons are both available from the same menu.
• Summon rates run from Rare (70.74%) down to Secret (0.01%).
• Claiming new Index entries, quests, achievements and the group award all pay Gems back.

Your first unit comes before your first summon

You do not start with an empty squad. The early tutorial grants your first starter unit — in one recorded session, the player's first pick was their "pebble frog" — before the game ever mentions summoning. Only after you have completed a round does the tutorial point you toward the outpost with the step "Welcome to the outpost! Your squad needs more units. Open SUMMON to call some in."

So the basic loop is: your starter arrives free, and summoning is how you add more units.

How to summon, step by step

1. Go to the outpost hub. Summoning lives at the SUMMON entry point there.
2. Open SUMMON.
3. Pick a banner. You can summon on the standard banner or on rotating and event banners (more on those below).
4. Choose single or x10. The menu shows SUMMON x10 for 500 Gems; single draws are also available at a smaller Gem cost.
5. Open units afterward. After a summon, the "Open units" button shows what you just pulled — one player's first x10 delivered a Legendary Dragon and a Blade Mantis straight into their unit list.

Two Settings toggles are useful if you summon in bulk: auto skip animation and auto sell. In recorded play, a player with both enabled still received the Index entry for every new discovery, so the discovery record is not lost by speeding past the animation.

What summons cost, and where Gems come from

Gems are the summon currency, so the practical question becomes how to keep earning them. The sources observed in the hub are:

• Index discoveries — every new unit discovery is recorded in the Index, and claiming new entries awards Gems. One player cleared a batch of unclaimed entries with "index claim all" and collected 360 Gems at once.
• Quests and achievements — the hub tracks these and pays Gems out as you complete them.
• The group claim — a Gems reward on the hub screen.

This makes summoning partly self-funding: each ten-pull adds discoveries, those discoveries can be claimed for Gems, and those Gems pay for the next batch. For a fuller list of sources, see the Gems guide and the currencies overview.

Summon rates

The rates screen lists five rarity tiers for summons:

In practice, most pulls land on Rare and Epic, Legendaries show up occasionally (the Dragon above came from an early x10), and Mythic and Secret units are genuine chase targets at 0.25% and 0.01%. We break the tiers down further in the unit rarities guide and cover hunting the rarest pulls in the Secret units guide.

Banners: standard, rotating and event

The summon screen uses selectable banners, and the banner you pick decides what pool you roll into:

• The standard banner is the default pool with the rates above.
• Rotating featured banners spotlight a specific unit — one player bought the "tiger banner" and chased a featured Mythic on it instead of using the standard pool.
• Event banners are summoned on using event-related play. During the Hollow Night event, the Units screen displayed event exclusives like Headless Horseman (Hollow Night / Secret, 0.02%) and Grim Reaper (Hollow Night / Mythic, 0.5%) — units tied to that event's banner rather than the standard pool.

The banner lineup and featured units rotate, so check what is currently featured before spending Gems; if a banner offers a unit you specifically want, targeting it beats rolling blindly on standard.

Checking what you got

Everything you pull ends up in two places. The Units screen holds your actual collection, filterable by ALL, RARE, EPIC, LEGENDARY, MYTHIC and SECRET — handy for confirming that a Mythic actually landed. The Index records each discovery; once an entry appears there, claim it for the Gem reward. For what each rarity tier contains, browse the full units list.