Experiment21 (21 for short) is a Mega Realm Boss in The Extended Tale of Diep, functioning as an area boss for the Erythea administrative region in the Realm of Sassafras. Idea by Diepmon.


21 is the first artificially created Hesperian, being entirely robotic instead of a cyborg like Sassafras JR. He was created by someone named "Daktor. Lakys" (apparently a codename for a Hesperian scientist, as Dr. Lacus clearly didn't make 21.) 21 has masculine programming and is fully sentient, and by that, is by definition a Hesperian. However, he's nowhere as efficient at gathering IE Energy as the Sassafras Supreme.

The Fight

Phase 1

21 can be found charging himself with solar panels in Erythea's northwestern outskirts, powered off. Players must disconnect his charging device to begin the fight. When that happens, 21 will turn on and immediately attack the player who pulled his plug.

21 has no special attacks in this phase, only (rather sluggishly) chasing down players, switching targets if players get out of his targeting range of 25 tiles. He fires Destroyer bullets rather slowly and spawns a maximum of 4 of his unique minions (seen in the image below) with a spawn cooldown of 15 seconds. His Minions have 800 health each and fire off large Sniper-style bullets that deal high damage and have high penetration, at the cost of a reload spanning 11 seconds.

Phase 2


21 in Phase 2, along with one of his minions.

At 13,000 health, 21 reveals more weapons previously hidden within his body and gains 30% damage reduction from added armor. He retains his simple AI from the last phase, but his four Auto Turrets can target players independent of his current target.

The main thing to watch out for is the Megabomber Cannon, which fires off large Bomber bombs that explode after 6 seconds of being fired and have an effective explosion radius of 12 tiles. These are aimed at the current player 21 himself is targeting.


  • I was thinking of adding a laser eye attack for 21, but since that's absurdly overused among Hesperians at this point, I decided against it.
  • If a Cytofras comes into view of 21 while he is battling, he will get confused, unable to process that this new arrival is both a Hesperian and not one at the same time (it's complicated, I'll explain later.)
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