Desert Biome

Desert, the third biome, sets the bar at 10K Speed, more than eleven times Lake's 900. The wiki notes it brings stronger guardians, and its own guardian proves the point: the Scorpion, a Mythic worth $18.5K/s whose egg takes 5 minutes and lists no Speed or cash reward.

Pets by rarity and income

• Jerboa (Common, $6/s, 20s egg) and Fennec (Uncommon, $18/s, 30s).
• Camel (Rare, $75/s) and Tob Tobi Tob Tob (Epic, $325/s).
• Snake (Legendary, $3.6K/s, 2m 30s egg).
• Sand Spider (Mythic, $16K/s) and Scorpion (Mythic, $18.5K/s).
• Royal Sphinx (Cosmic, $280K/s, 30-minute egg).

Royal Sphinx is the top earner and third of the 28 Cosmics, a little above Lake's Leviathan. The Sand Spider is the lowest-earning Mythic in the whole game, yet it still makes more than four Snakes combined.

The Speed maths to reach Jungle

Jungle requires 40K Speed, a 30K gap from Desert's entry point. Desert rewards range from +7.2k (Jerboa) to +18k (Royal Sphinx):

1. Five Jerboa eggs (+7.2k each) give 36k after 100 seconds of total growth. At roughly 360 Speed per second of growth, the Jerboa has the best ratio of any egg up to this point.
2. Three Snakes (+10.8k each) give 32.4k, with 2m 30s per egg.
3. Two Royal Sphinx eggs (+18k each) reach 36k, but each one takes half an hour.

The Scorpion is the only Desert egg with no reward listed, so as far as the wiki documents it adds nothing to your Speed total.

Income ceiling with mutations

Using the wiki's formula, a Rainbow Royal Sphinx (×3.5) would reach about $980K/s, and a roll at 100× the base weight multiplies base value roughly 17 times. Treat those as estimates: the wiki itself labels its calculator as beta.

On the cash side, a Sand Spider reward pays $1.6m, so three of them cover the Celebrity Treadmill ($5M), which gives +30 Speed per step. That treadmill is the one that keeps paying off through the next two biomes.