Ravager doesnt care whether the +1/+1 counters on it are from Overseer or from its own ability, so they can all modular onto another creature just the same
Here's a look at some of the most exciting products we can expect from the Pokmon 30th anniversary set and its associated collections

3 Angraecum Umbrella 3 Revealer of the Ice Barrier 3 Speaker for the Ice Barriers 1 Warlock of the Ice Barrier 3 Prior of the Ice Barrier 2 Zuijin of the Ice Barrier 2 Hexa Spirit of the Ice Barrier 3 General Wayne of the Ice Barrier 3 Deep Sea Diva 3 Winds Over the Ice Barrier 3 Medallion of the Ice Barrier 1 Freezing Chains of the Ice Barrier 3 Deep Sea Aria 1 Monster Reborn 3 Terror of Trishula 3 The Frozen God 1 Tatsunoko 1 Crystron Quandax 1 Brionac, Dragon of the Ice Barrier 1 Dewloren, Tiger King of the Ice Barrier 1 Coral Dragon 1 Deep Sea Prima Donna 1 Gungnir, Dragon of the Ice Barrier 1 Shooting Riser Dragon 1 White Aura Whale 1 Ravenous Crocodragon Archethys 1 Crystron Quariongandrax 1 Trishula, Dragon of the Ice Barrier 1 Trishula, Zero Dragon of the Ice Barrier 1 White Aura Bihamut 1 Crystron Halqifibrax Deck 2: Rose Dragon Deck Featuring Samsara Lotus Samsara Lotus Special Summons itself during the End Phase, which can be Tributed for Crossrose Dragon, as well as the effect of Staysailor Romaryn

The card is particularly good in decks that meet the stipulation without trying very hard
It is certainly an entertaining card and there are some cool interactions that are currently played, such as the Dress Down combo which annuls Deaths Shadows ability and makes him a straight up 13/13
So it works as a bit of a letdown as you play with it