Here's a list of portal bosses in version 3.2.

Boss Portal Cost Level Reward
Allied Scrub Allied training paper 5 beastmen seals 10 250
Gato Millennial fair pass 10 beastmen seals 10 500
Morion Worm Worm food 5 beastmen seals 25 250
Armos Knight Armos medallian 15 beastmen seals 30 750
Crazy Jester Demon bell 10 beastmen seals 30 500
Mazaal Mayan map 20 beastmen seals 30 1000
Moldorm Hera key 15 beastmen seals 30 750
Lanmolas Book of mudora 15 beastmen seals 30 750
Time Bomb Bomb shard 10 beastmen seals 30 500
Eye of Cthulhu Suspicious looking eye 15 beastmen seals 50 750
Poison Virility can 15 beastmen seals 50 750
Brain of Cthulhu Bloody spine 15 beastmen seals 75 750
Eater of Worlds Corrupt worm food 15 beastmen seals 75 750
Skeletron Dungeon map 15 beastmen seals 100 750
Rasetsu, Gaki, Onki Banishing charm 20 kindred seals 50 2000
Leviathan Ignis fatuus 20 kindred seals 55 2000
Bob Barbas News orb 20 kindred seals 60 2000
Legion Rotting orb 25 kindred seals 100 2500
Byakko Gem of the West 15 kindred seals 110 1500
Genbu Gem of the North 15 kindred seals 110 1500
Seiryu Gem of the East 15 kindred seals 110 1500
Suzaku Gem of the South 15 kindred seals 110 1500
Awahondo Avatar blood 20 kindred seals 150 2000
Gamma Energy elements 15 kindred seals 150 1500
Huu Xalmo the Savage Yagudo drink 20 kindred seals 150 2000
Ironclad Severer Spheroid plate 20 kindred seals 150 2000
Marchelute Tavnazia pass 20 kindred seals 150 2000
Prozpuz Old orc bow 20 kindred seals 150 2000
Rainemard Lachesis orb 20 kindred seals 150 2000
Smelter Demon Smelter demon soul 20 kindred seals 150 2000
The Twins Mechanical eye 15 kindred seals 200 1500
The Destroyer Mechanical worm 15 kindred seals 200 1500
Skeletron Prime Mechanical skull 15 kindred seals 225 1500
Plantera Plantera's bulb 15 kindred seals 250 1500
Eccentric Eve* Jungle orb 20− kindred crests 150 2000
Echidna* Jungle orb 20− kindred crests 150 2000
Geryon Time orb 20 kindred crests 150 2000
Gwajboj Old orc sword 20 kindred crests 150 2000
I-No Evil guitar 20 kindred crests 200 2000
Lihzahrd Golem Lihzahrd power cell 15 kindred crests 250 1500
Duke Fishron Truffle worm 15 kindred crests 275 1500
Shinryu Verus Crimson traverser stone 20 kindred crests 275 2000
Obito Uchiha Strange mask 20 kindred crests 300 2000
Ashi Atora Atlantian crystal 20 high kindred crests 300 3000
Freya, Sif Goddess orb 20 high kindred crests 300 3000
Old Iron King Old king soul 20 high kindred crests 400 3000
Madara Uchiha Gunbai 20 high kindred crests 500 3000
Zemus Strange crystal 20 high kindred crests 1000 3000
The Broken One, Obsolete Mule Obsolete orb 20 high kindred crests 2000 3000
The Witch, The Crazzy, The Monster Decayed orb 20 high kindred crests 2000 3000
Asriel Dreemurr Barrier orb 20 high kindred crests 50000 5000
Shadow Jester Shadow demon bell 5 high kindred crests 250 1000
Shadow Ashi Shadow atlantian crystal 20 high kindred crests 7500 5000
Shadow Kirin Shadow god seal 10 high kindred crests 1550 2500
Hero of Time Hyrule orb Crafting only 100 3000
Kirin God seal Crafting only 120 3000
Grahf Unknown power source Crafting only 300 3000
Rusalkas Fortuna crest Crafting only 5000 5000
Calcabrina Anti-doll charm Crafting only 5000 5000
Ifrit Prime Bowl of embers Crafting only 5000 5000

Rewards are in allied notes.

* The jungle orb will summon either Eccentric Eve or Echidna, at random.

– If the Allied Forces garden is at or above level 5, the price of the jungle orb will be 15 kindred crests. Due to what is presumably a bug in Battle Arena 2.6, up to that version this discount is given if the garden is at or below level 5.