The Castle Victoria node is upstairs in the castle, the safest node in the game to bond with.
Where it is
Upstairs in Castle Victoria. The marked map is on the location page: Upstairs in Castle Victoria.
Getting it
Walk in and use it. Because it sits inside town walls it is the node most players get first.
Melding
Stand within three squares of the node and use it. The bond raises your maximum mana by three points plus one for every ten points of Mysticism above five, so between three and eight depending on how mystical you are. You can bond with each node once, and the game will list the ones you hold if you ask.
This node can be drained by the Xeochicatl. See Nodes for what happens when one is attacked.