diff --git a/lib/glacier/status/error_or.h b/lib/glacier/status/error_or.h
index cbdc158..ca0c85a 100644
--- a/lib/glacier/status/error_or.h
+++ b/lib/glacier/status/error_or.h
@@ -32,12 +32,15 @@ class ErrorOr {
   bool ok_;
 };
 
-#define ASSIGN_OR_RETURN(lhs, rhs) \
-                                   \
-  auto e##__LINE__ = rhs;          \
-  if (!e##__LINE__.ok()) {         \
-    return e##__LINE__.error();    \
-  }                                \
+#define AOR_INNER(a, b) a##b
+#define AOR_VAR(a) AOR_INNER(e, a)
+
+#define ASSIGN_OR_RETURN(lhs, rhs)    \
+                                      \
+  auto AOR_VAR(__LINE__) = rhs;       \
+  if (!AOR_VAR(__LINE__).ok()) {      \
+    return AOR_VAR(__LINE__).error(); \
+  }                                   \
   lhs = rhs.value();
 
 }  // namespace glcr
diff --git a/lib/mammoth/CMakeLists.txt b/lib/mammoth/CMakeLists.txt
index e8ba624..8edb58e 100644
--- a/lib/mammoth/CMakeLists.txt
+++ b/lib/mammoth/CMakeLists.txt
@@ -1,6 +1,8 @@
 add_library(mammoth_lib STATIC
   src/channel.cpp
   src/debug.cpp
+  src/endpoint_client.cpp
+  src/endpoint_server.cpp
   src/init.cpp
   src/memory_region.cpp
   src/process.cpp
diff --git a/lib/mammoth/include/mammoth/endpoint_client.h b/lib/mammoth/include/mammoth/endpoint_client.h
new file mode 100644
index 0000000..9b54933
--- /dev/null
+++ b/lib/mammoth/include/mammoth/endpoint_client.h
@@ -0,0 +1,37 @@
+#pragma once
+
+#include <glacier/container/pair.h>
+#include <glacier/status/error_or.h>
+#include <zcall.h>
+#include <ztypes.h>
+
+class EndpointClient {
+ public:
+  static EndpointClient AdoptEndpoint(z_cap_t cap);
+
+  template <typename Req, typename Resp>
+  glcr::ErrorOr<glcr::Pair<Resp, z_cap_t>> CallEndpoint(const Req& req);
+
+ private:
+  EndpointClient(uint64_t cap) : cap_(cap) {}
+  z_cap_t cap_;
+};
+
+template <typename Req, typename Resp>
+glcr::ErrorOr<glcr::Pair<Resp, z_cap_t>> EndpointClient::CallEndpoint(
+    const Req& req) {
+  uint64_t reply_port_cap;
+  RET_ERR(ZEndpointSend(cap_, sizeof(Req), &req, &reply_port_cap));
+
+  Resp resp;
+  z_cap_t cap = 0;
+  uint64_t num_caps = 1;
+  uint64_t num_bytes = sizeof(Resp);
+  RET_ERR(ZReplyPortRecv(reply_port_cap, &num_bytes, &resp, &num_caps, &cap));
+
+  if (num_bytes != sizeof(resp) || num_caps != 1) {
+    return glcr::FAILED_PRECONDITION;
+  }
+
+  return glcr::Pair{resp, cap};
+}
diff --git a/lib/mammoth/include/mammoth/endpoint_server.h b/lib/mammoth/include/mammoth/endpoint_server.h
new file mode 100644
index 0000000..51af6c3
--- /dev/null
+++ b/lib/mammoth/include/mammoth/endpoint_server.h
@@ -0,0 +1,22 @@
+#pragma once
+
+#include <glacier/status/error_or.h>
+#include <ztypes.h>
+
+#include "mammoth/endpoint_client.h"
+
+class EndpointServer {
+ public:
+  static glcr::ErrorOr<EndpointServer> Create();
+  static EndpointServer Adopt(z_cap_t endpoint_cap);
+
+  glcr::ErrorOr<EndpointClient> CreateClient();
+
+  // FIXME: Release Cap here.
+  z_cap_t GetCap() { return endpoint_cap_; }
+
+ private:
+  z_cap_t endpoint_cap_;
+
+  EndpointServer(z_cap_t cap) : endpoint_cap_(cap) {}
+};
diff --git a/lib/mammoth/include/mammoth/process.h b/lib/mammoth/include/mammoth/process.h
index a331422..b853ae1 100644
--- a/lib/mammoth/include/mammoth/process.h
+++ b/lib/mammoth/include/mammoth/process.h
@@ -3,6 +3,6 @@
 #include <glacier/status/error_or.h>
 #include <stdint.h>
 
-#include "mammoth/channel.h"
+#include "mammoth/endpoint_client.h"
 
-glcr::ErrorOr<Channel> SpawnProcessFromElfRegion(uint64_t program);
+glcr::ErrorOr<EndpointClient> SpawnProcessFromElfRegion(uint64_t program);
diff --git a/lib/mammoth/src/endpoint_client.cpp b/lib/mammoth/src/endpoint_client.cpp
new file mode 100644
index 0000000..7af836b
--- /dev/null
+++ b/lib/mammoth/src/endpoint_client.cpp
@@ -0,0 +1,3 @@
+#include "mammoth/endpoint_server.h"
+
+EndpointClient EndpointClient::AdoptEndpoint(z_cap_t cap) { return {cap}; }
diff --git a/lib/mammoth/src/endpoint_server.cpp b/lib/mammoth/src/endpoint_server.cpp
new file mode 100644
index 0000000..071ddab
--- /dev/null
+++ b/lib/mammoth/src/endpoint_server.cpp
@@ -0,0 +1,14 @@
+#include "mammoth/endpoint_server.h"
+
+glcr::ErrorOr<EndpointServer> EndpointServer::Create() {
+  uint64_t cap;
+  RET_ERR(ZEndpointCreate(&cap));
+  return EndpointServer(cap);
+}
+
+glcr::ErrorOr<EndpointClient> EndpointServer::CreateClient() {
+  uint64_t client_cap;
+  // FIXME: Restrict permissions to send-only here.
+  RET_ERR(ZCapDuplicate(endpoint_cap_, &client_cap));
+  return EndpointClient::AdoptEndpoint(client_cap);
+}
diff --git a/lib/mammoth/src/process.cpp b/lib/mammoth/src/process.cpp
index 068cd88..267a991 100644
--- a/lib/mammoth/src/process.cpp
+++ b/lib/mammoth/src/process.cpp
@@ -3,8 +3,8 @@
 #include <glacier/status/error.h>
 #include <zcall.h>
 
-#include "mammoth/channel.h"
 #include "mammoth/debug.h"
+#include "mammoth/endpoint_server.h"
 #include "mammoth/init.h"
 #include "mammoth/port.h"
 
@@ -95,20 +95,21 @@ uint64_t LoadElfProgram(uint64_t base, uint64_t as_cap) {
 
 }  // namespace
 
-glcr::ErrorOr<Channel> SpawnProcessFromElfRegion(uint64_t program) {
-  Channel local, foreign;
-  check(CreateChannels(local, foreign));
+glcr::ErrorOr<EndpointClient> SpawnProcessFromElfRegion(uint64_t program) {
+  ASSIGN_OR_RETURN(EndpointServer server, EndpointServer::Create());
+  ASSIGN_OR_RETURN(EndpointClient client, server.CreateClient());
 
   uint64_t proc_cap;
   uint64_t as_cap;
   uint64_t foreign_port_id;
   uint64_t port_cap;
+
 #if MAM_PROC_DEBUG
   dbgln("Port Create");
 #endif
-  check(ZPortCreate(&port_cap));
+  RET_ERR(ZPortCreate(&port_cap));
   uint64_t port_cap_donate;
-  check(ZCapDuplicate(port_cap, &port_cap_donate));
+  RET_ERR(ZCapDuplicate(port_cap, &port_cap_donate));
 
 #if MAM_PROC_DEBUG
   dbgln("Spawn");
@@ -127,12 +128,12 @@ glcr::ErrorOr<Channel> SpawnProcessFromElfRegion(uint64_t program) {
   Port p(port_cap);
   check(p.WriteMessage<uint64_t>(Z_INIT_SELF_PROC, proc_cap));
   check(p.WriteMessage<uint64_t>(Z_INIT_SELF_VMAS, as_cap));
-  check(p.WriteMessage<uint64_t>(Z_INIT_CHANNEL, foreign.release_cap()));
+  check(p.WriteMessage<uint64_t>(Z_INIT_CHANNEL, server.GetCap()));
 
 #if MAM_PROC_DEBUG
   dbgln("Thread start");
 #endif
   check(ZThreadStart(thread_cap, entry_point, foreign_port_id, 0));
 
-  return local;
+  return client;
 }
diff --git a/sys/denali/client/denali_client.cpp b/sys/denali/client/denali_client.cpp
index fcda77d..07af87d 100644
--- a/sys/denali/client/denali_client.cpp
+++ b/sys/denali/client/denali_client.cpp
@@ -4,18 +4,21 @@
 
 #include "denali/denali.h"
 
-MappedMemoryRegion DenaliClient::ReadSectors(uint64_t device_id, uint64_t lba,
-                                             uint64_t num_sectors) {
+glcr::ErrorOr<MappedMemoryRegion> DenaliClient::ReadSectors(
+    uint64_t device_id, uint64_t lba, uint64_t num_sectors) {
   DenaliRead read{
       .device_id = device_id,
       .lba = lba,
       .size = num_sectors,
   };
-  check(channel_.WriteStruct(&read));
+  auto pair_or = endpoint_.CallEndpoint<DenaliRead, DenaliReadResponse>(read);
+  if (!pair_or) {
+    return pair_or.error();
+  }
+  auto pair = pair_or.value();
 
-  DenaliReadResponse resp;
-  uint64_t mem_cap;
-  check(channel_.ReadStructAndCap(&resp, &mem_cap));
+  DenaliReadResponse& resp = pair.first();
+  z_cap_t& mem_cap = pair.second();
 
   return MappedMemoryRegion::FromCapability(mem_cap);
 }
diff --git a/sys/denali/include/denali/denali_client.h b/sys/denali/include/denali/denali_client.h
index 7a91403..f660289 100644
--- a/sys/denali/include/denali/denali_client.h
+++ b/sys/denali/include/denali/denali_client.h
@@ -1,15 +1,17 @@
 #pragma once
 
-#include <mammoth/channel.h>
+#include <glacier/status/error_or.h>
+#include <mammoth/endpoint_client.h>
 #include <mammoth/memory_region.h>
 
 class DenaliClient {
  public:
-  DenaliClient(const Channel& channel) : channel_(channel) {}
+  DenaliClient(const EndpointClient& endpoint) : endpoint_(endpoint) {}
 
-  MappedMemoryRegion ReadSectors(uint64_t device_id, uint64_t lba,
-                                 uint64_t num_sectors);
+  glcr::ErrorOr<MappedMemoryRegion> ReadSectors(uint64_t device_id,
+                                                uint64_t lba,
+                                                uint64_t num_sectors);
 
  private:
-  Channel channel_;
+  EndpointClient endpoint_;
 };
diff --git a/sys/yellowstone/hw/gpt.cpp b/sys/yellowstone/hw/gpt.cpp
index e68ca47..bce2360 100644
--- a/sys/yellowstone/hw/gpt.cpp
+++ b/sys/yellowstone/hw/gpt.cpp
@@ -49,8 +49,9 @@ struct PartitionEntry {
 
 GptReader::GptReader(const DenaliClient& client) : denali_(client) {}
 
-z_err_t GptReader::ParsePartitionTables() {
-  MappedMemoryRegion lba_1_and_2 = denali_.ReadSectors(0, 0, 2);
+glcr::ErrorCode GptReader::ParsePartitionTables() {
+  ASSIGN_OR_RETURN(MappedMemoryRegion lba_1_and_2,
+                   denali_.ReadSectors(0, 0, 2));
   uint16_t* mbr_sig = reinterpret_cast<uint16_t*>(lba_1_and_2.vaddr() + 0x1FE);
   if (*mbr_sig != 0xAA55) {
     return glcr::FAILED_PRECONDITION;
@@ -83,8 +84,9 @@ z_err_t GptReader::ParsePartitionTables() {
   dbgln("partition_entry_size: %x", entry_size);
   dbgln("Num blocks: %x", num_blocks);
 
-  MappedMemoryRegion part_table =
-      denali_.ReadSectors(0, header->lba_partition_entries, num_blocks);
+  ASSIGN_OR_RETURN(
+      MappedMemoryRegion part_table,
+      denali_.ReadSectors(0, header->lba_partition_entries, num_blocks));
   dbgln("Entries");
   for (uint64_t i = 0; i < num_partitions; i++) {
     PartitionEntry* entry = reinterpret_cast<PartitionEntry*>(
diff --git a/sys/yellowstone/hw/gpt.h b/sys/yellowstone/hw/gpt.h
index 2d7fe05..8a6da3f 100644
--- a/sys/yellowstone/hw/gpt.h
+++ b/sys/yellowstone/hw/gpt.h
@@ -8,7 +8,7 @@ class GptReader {
  public:
   GptReader(const DenaliClient&);
 
-  z_err_t ParsePartitionTables();
+  glcr::ErrorCode ParsePartitionTables();
 
  private:
   DenaliClient denali_;
diff --git a/sys/yellowstone/yellowstone.cpp b/sys/yellowstone/yellowstone.cpp
index fd898a6..341567c 100644
--- a/sys/yellowstone/yellowstone.cpp
+++ b/sys/yellowstone/yellowstone.cpp
@@ -1,6 +1,6 @@
 #include <denali/denali.h>
-#include <mammoth/channel.h>
 #include <mammoth/debug.h>
+#include <mammoth/endpoint_client.h>
 #include <mammoth/init.h>
 #include <mammoth/process.h>
 #include <zcall.h>
@@ -17,13 +17,13 @@ uint64_t main(uint64_t port_cap) {
   uint64_t vaddr;
   check(ZAddressSpaceMap(gSelfVmasCap, 0, gBootDenaliVmmoCap, &vaddr));
 
-  auto local_or = SpawnProcessFromElfRegion(vaddr);
-  if (!local_or) {
-    check(local_or.error());
+  auto endpoint_or = SpawnProcessFromElfRegion(vaddr);
+  if (!endpoint_or) {
+    check(endpoint_or.error());
   }
-  Channel local = local_or.value();
+  EndpointClient endpoint = endpoint_or.value();
 
-  DenaliClient client(local);
+  DenaliClient client(endpoint);
   GptReader reader(client);
 
   check(reader.ParsePartitionTables());
diff --git a/zion/include/zcall.h b/zion/include/zcall.h
index 16e7452..c666dca 100644
--- a/zion/include/zcall.h
+++ b/zion/include/zcall.h
@@ -123,6 +123,16 @@ SYS5(PortPoll, z_cap_t, port_cap, uint64_t*, num_bytes, void*, data, uint64_t*,
 
 SYS2(IrqRegister, uint64_t, irq_num, z_cap_t*, port_cap);
 
+SYS1(EndpointCreate, z_cap_t*, endpoint_cap);
+SYS4(EndpointSend, z_cap_t, endpoint_cap, uint64_t, num_bytes, const void*,
+     data, z_cap_t*, reply_port_cap);
+SYS4(EndpointRecv, z_cap_t, endpoint_cap, uint64_t*, num_bytes, void*, data,
+     z_cap_t*, reply_port_cap);
+SYS5(ReplyPortSend, z_cap_t, reply_port_cap, uint64_t, num_bytes, const void*,
+     data, uint64_t, num_caps, z_cap_t*, caps);
+SYS5(ReplyPortRecv, z_cap_t, reply_port_cap, uint64_t*, num_bytes, const void*,
+     data, uint64_t*, num_caps, z_cap_t*, caps);
+
 SYS2(CapDuplicate, z_cap_t, cap_in, z_cap_t*, cap_out);
 
 SYS1(Debug, const char*, message);
diff --git a/zion/include/ztypes.h b/zion/include/ztypes.h
index 55d2ca3..a58535a 100644
--- a/zion/include/ztypes.h
+++ b/zion/include/ztypes.h
@@ -41,6 +41,13 @@ const uint64_t kZionPortPoll = 0x53;
 
 const uint64_t kZionIrqRegister = 0x58;
 
+const uint64_t kZionEndpointCreate = 0x60;
+const uint64_t kZionEndpointSend = 0x61;
+const uint64_t kZionEndpointRecv = 0x62;
+const uint64_t kZionReplyPortSend = 0x63;
+const uint64_t kZionReplyPortRecv = 0x64;
+const uint64_t kZionEndpointCall = 0x65;
+
 #define Z_IRQ_PCI_BASE 0x30
 
 // Capability Calls