Lord Holy Angemon
Lord Holy Angemon is a Holy Angemon that opposes Demon and trains Digimon to defeat him. He's also one of the support programs of the Digital World. He called Taichi to the Digital World in the belief that only a Tamer and his Digimon would be able to defeat the evil Demon, and sent them to gather the five Tamer Tags they would need to gather to enter Demon's Castle, which had once belonged to the God of the Digital World, who hated humans. Lord Holy Angemon could evolve to Seraphimon at any time he wanted, but when he was defeated by Arkadimon Adult, his Win Ratio was lowered and thus he could only evolve into Dominimon, a weaker angel Digimon with shields on his arms. During that same battle, he put on his battle suit and looked like normal Holy Angemon do.
Shogun Gekomon is a Digimon working for or with Holy Angemon; it's not quite clear. He doubted the ability of Taichi and Zero to defeat Demon, but after they dispelled his attack, he accepted them.
Leo the Leomon
Leo was a Digimon in charge of training Lord Holy Angemon's troops - Taichi and Zero thought he was too harsh, and tried to tell him off, but ended up fighting one of his trained Digimon to see if Digimon with Tamers were really better. Leo's Kuwagamon was defeated, and he eventually became friends with Taichi and Zero. He also evolved to Panjyamon to fight a Venom Vamdemon sent by Demon, and later once more to Regulumon.
Whamon, like Holy Angemon, was once one of the Support Programs of the Digital World. However, he was very old, and when Taichi and Zero arrived, he died to give them a Digivice 01.