[BT4-114] Ancient Garurumon is a very under-use secret rare card when he is introduced in BT4 Great Legends. The problem is, the cost to evolve into him is over-priced to pay, paying 5 cost to just evolve into a LV6 digimon seems not really "friendly" for the game control, that is why no Tamer use him in BT4 meta.
Only when a promo card comes to help AncientGaruru showing its value, only then people starts to put him into the deck instead of leaving him sleep in the binder.
Before this promo Lobomon, we already had 4 type of blue hybrid digimon, those are LV3 Strabimon with the effect to search for hybrid digimon and blue tamer from deck to put to hand, the [BT4-025] Lobomon to evolve into a tamer with 2 cost or another LV4 hybrid Garummon (3 cost to evolve, so we rarely use him), LV5 hybrid is Beowolfmon – a very good LV5 to use in any blue deck, especially the hybrid-focused deck.
Come back to the combo with AncientGarurumon, the promo [P-030] Lobomon can evolve into AncientGarurumon when evolving from a LV3 digimon by paying 1 cost. So for this digivolution from LV2 to LV6, we have to pay total 3 cost to get AncientGaruru into the battle (Be aware that the "When digivolving" effect is only valid in the battle, not in raising area).
After evolved into AncientGaruru, this digimon can declare attack and trigger its "when attacking" effect to unsuspend 2 of your digimon with name "Garurumon" or a hybrid digimon. For this deck, all the above hybrid digimon are necessary to form a deck that constantly focus on using "hybrid" benefits, the Beowolfmon with "jamming" can survive after attack opponent's security, then unsuspend by using AncentGaruru "when attacking" effect, the LV4 BT4 Lobomon can be a final surprised attack to end the game when we evolve him from a blue tamer or to free-summon when AncientGaruru is deleted.
Another strategy to use the combo of AncientGarurumon, promo Lobomon and Weregarurumon is posted in one of our post "Finally, AncientGarurumon is highly hunted" that you can refer to.