Bestfriend Telecard (親友テレカ Shin'yū Tereka) is a legendary relic that has been said to possess power beyond comprehension. There are seven cards in total, and all of them were held by the members of The Doraemons.
In order to activate the cards, all seven bearers must swear under the oath of eternal friendship; by words and by heart.
How to obtain
They were sealed deep inside a colossal ruins. A subterranean labyrinth was buried under the ruins, with traps scattered thorough every corner. The cards lie in 3 different chambers; where each is surrounded by lethal traps.
The cards work like an ordinary telephone. The difference is the fact that it functions anywhere and anytime, by means of telepathy; reserved only to those who possess them. When one of the bearers are in dire situations; it acts as a distress signal, in which it radiates, signaling all the members to gather.
It has been numerously shown that the powers combined through all seven cards; could enhance the power of an object (where usually it gets bigger), fast-forward a growth, and potentially be a source of unlimited energy.